Plane wave-based illumination system and exposure equipment

Abstract

The present invention relates to the technical field of holographic lithography systems, and discloses a plane wave-based illumination system and exposure equipment, comprising: a first lens group and a second lens group arranged sequentially along an optical axis; the first lens group is used to expand the laser light output by a light source; the second lens group is used to collimate the expanded laser light and output the plane wave laser light toward a holographic mask; the distance between the first lens group and the second lens group is the sum of the effective focal lengths of the first lens group and the second lens group. By expanding the light beam by the first lens group and then collimating the light beam by the second lens group, the lens group can reduce wavefront aberrations of the illumination system, thereby improving lithography resolution. Compared with traditional projection lithography illumination systems and holographic mask illumination systems based on spherical waves, the system can reduce the number of lenses used, thereby reducing manufacturing costs.

Description

Technical Field

[0001] The present invention relates to the technical field of holographic lithography, and in particular to an illumination system and exposure equipment based on plane waves. Background Art

[0002] Among the key equipment in large-scale integrated circuit manufacturing, the lithography system is a crucial component. It uses lasers to image mask patterns onto silicon wafers. In traditional projection lithography, the 193nm operating wavelength projection lithography objective lens is the core component of projection lithography systems for producing ultra-fine patterns.

[0003] In the field of traditional projection lithography, projection lithography lenses operating in the 193nm wavelength band are core components of projection lithography devices used to produce ultra-fine patterns. However, these lenses are complex in structure, and most feature advanced aspheric surfaces. This results in a large system size and requires a high level of manufacturing and integrated assembly processes. For example, patent US20030030916A1 describes a projection lithography lens with a maximum numerical aperture of 0.89. The lens comprises at least four groups of lenses, totaling 29 elements. Each group has either positive or negative optical power, requiring multiple lens groups to expand and focus the light beam multiple times. Therefore, new, low-cost, highly integrated lithography technologies will promote the development of both the lithography and semiconductor fields.

[0004] Holographic lithography systems, used in integrated circuit manufacturing, utilize lasers to image holographic mask patterns onto substrates such as silicon wafers. Compared to projection lithography, holographic lithography requires less complex illumination systems. Since there is no object-image relationship between the mask and the silicon wafer, it avoids the reliance on projection lenses required by conventional projection lithography. The performance of the holographic illumination system is crucial in holographic lithography, directly determining the pattern transfer capabilities of the entire exposure apparatus. Summary of the Invention

[0005] In view of this, the present invention provides an illumination system and exposure equipment based on plane waves, which can overcome at least one of the technical problems of the prior art illumination system, such as the complex structure and the inability to meet the requirements of plane wave holographic lithography.

[0006] A first aspect of the present invention provides a plane wave-based illumination system for use in holographic lithography, comprising: a first lens group and a second lens group arranged in sequence along an optical axis; the first lens group is used to expand the laser output by a light source; the second lens group is used to collimate the expanded laser and output the plane wave laser in the direction of a holographic mask; the distance between the first lens group and the second lens group is the sum of the effective focal length of the first lens group and the effective focal length of the second lens group.

[0007] Optionally, the first lens group and the second lens group satisfy:

[0008]

[0009] Among them, f1 ′ is the effective focal length of the first lens group, f2 is the effective focal length of the second lens group, and M is the magnification of the illumination system.

[0010] Optionally, the first lens group includes a first negative lens, a second negative lens and a third negative lens arranged in sequence along the optical axis; the light-entry surface of the first negative lens has a negative curvature radius, which is used to receive the laser output by the light source and perform the first beam expansion, and the light-exit surface of the first negative lens is a plane, which is used to maintain the light track of the laser beam expansion; the light-entry surface of the second negative lens has a negative curvature radius, which is used to perform a second beam expansion on the laser incident through the first negative lens, and the light-exit surface of the second negative lens is a plane, which is used to maintain the light track of the laser beam expansion; the light-entry surface of the third negative lens has a negative curvature radius, which is used to perform a third beam expansion on the laser incident through the second negative lens, and the light-exit surface of the third negative lens is a plane, which is used to maintain the light track of the laser beam expansion.

[0011] Optionally, the first negative lens, the second negative lens and the third negative lens satisfy the following conditions:

[0012] |r11|=|r21|=|r31|, and |r12|=|r22|=|r32|;

[0013] Among them, r11 and r12 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the first negative lens respectively, r21 and r22 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the second negative lens respectively, and r31 and r32 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the third negative lens respectively.

[0014] Optionally, the distance D between the first negative lens and the second negative lens is 12 and the distance D between the second negative lens and the third negative lens 23 Satisfied: D 12 <D 23 .

[0015] Optionally, the effective focal length f1 of the first lens group is ′ satisfy:

[0016]

[0017] Among them, F1 ′ 2 is the combined focal length of the first negative lens and the second negative lens, f1 ′ 3 is the effective focal length of the third negative lens, D 23is the distance between the second negative lens and the third negative lens; wherein the combined focal length F1 of the first negative lens and the second negative lens ′ 2 Satisfaction:

[0018]

[0019] Where f1 ′ 1 is the effective focal length of the first negative lens, f1 ′ 2 is the effective focal length of the second negative lens, D 12 is the distance between the first negative lens and the second negative lens.

[0020] Optionally, the effective focal length f1 of the first negative lens is ′ 1. The effective focal length f1 of the second negative lens ′ 2 and the effective focal length f1 of the third negative lens ′ 3 Satisfaction:

[0021]

[0022]

[0023]

[0024] Among them, n is the refractive index of the lens material, r11 and r12 are the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the first negative lens respectively, d11 is the thickness of the first negative lens, r21 and r22 are the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the second negative lens respectively, d12 is the thickness of the second negative lens, r31 and r32 are the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the third negative lens respectively, and d13 is the thickness of the third negative lens.

[0025] Optionally, the second lens group includes a first meniscus lens, a second meniscus lens and a first positive lens arranged in sequence along the optical axis; the light entrance surface and the light exit surface of the first meniscus lens both have a negative curvature radius, and the first meniscus lens is used to perform a first collimation on the laser incident through the first lens group; the light entrance surface and the light exit surface of the second meniscus lens both have a negative curvature radius, and the second meniscus lens is used to perform a second collimation on the laser incident through the first meniscus lens; the light entrance surface and the light exit surface of the first positive lens both have a negative curvature radius, and the first positive lens is used to perform a third collimation on the laser incident through the second meniscus lens.

[0026] Optionally, the first meniscus lens, the second meniscus lens and the first positive lens satisfy the following conditions:

[0027] |r61|>|r51|>|r41|, and |r62|>|r52|>|r42|;

[0028] Among them, r41 and r42 are the curvature radius of the light incident surface and the curvature radius of the light exit surface of the first meniscus lens respectively, r51 and r52 are the curvature radius of the light incident surface and the curvature radius of the light exit surface of the second meniscus lens respectively, and r61 and r62 are the curvature radius of the light incident surface and the curvature radius of the light exit surface of the first positive lens respectively.

[0029] Optionally, the distance D between the first meniscus lens and the second meniscus lens is 45 Satisfies: 15mm<D 45 <16mm; the distance D between the second meniscus lens and the first positive lens 56 Satisfies: 15mm<D 56 <16mm.

[0030] Optionally, the effective focal length f2 of the second lens group satisfies:

[0031]

[0032] Among them, F4 ′ 5 is the combined focal length of the first meniscus lens and the second meniscus lens, f2 ′ 3 is the effective focal length of the first positive lens, D 56 is the distance between the second meniscus lens and the first positive lens;

[0033] The combined focal length of the first meniscus lens and the second meniscus lens is F4 ′ 5 Satisfaction:

[0034]

[0035] Among them, f2 ′ 1 is the effective focal length of the first meniscus lens, f2 ′ 2 is the effective focal length of the second meniscus lens, D 45 is the distance between the first meniscus lens and the second meniscus lens.

[0036] Optionally, the effective focal length f2 of the first meniscus lens is ′ 1. The effective focal length f2 of the second meniscus lens ′ 2 and the effective focal length f2 of the first positive lens ′ 3 Satisfaction:

[0037]

[0038]

[0039]

[0040] Among them, r41 and r42 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the first meniscus lens respectively, d21 is the thickness of the first meniscus lens, r51 and r52 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the second meniscus lens respectively, d22 is the thickness of the second meniscus lens, r61 and r62 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the first positive lens respectively, and d23 is the thickness of the first positive lens.

[0041] Optionally, the lighting system further includes a compensation mechanism, which is connected to the third negative lens, and is used to drive the third negative lens to move along the optical axis between the second negative lens and the second lens group. The movement range Δl of the third negative lens satisfies the following with reference to the starting position of the third negative lens: -1.0mm≤Δl≤+1.0mm.

[0042] Optionally, an aperture is provided between the first lens group and the second lens group, and a distance between the aperture and the first lens group is greater than a distance between the aperture and the second lens group.

[0043] A second aspect of the present invention provides an exposure device for use in a chip manufacturing process, comprising the plane wave-based illumination system described in any one of the first aspects.

[0044] The plane wave-based illumination system and exposure equipment of the present invention have at least the following beneficial effects:

[0045] In the plane wave-based illumination system and exposure equipment of the present invention, after the light beam emitted by the light source strikes the first lens group, the first lens group expands the beam. The second lens group then collimates the expanded laser light to produce collimated light. The beam propagates in the form of a plane wave toward the holographic mask, and then projects the image of the holographic mask onto the silicon wafer. By expanding the beam by the first lens group and then collimating it by the second lens group, the lens system, which first expands the beam and then collimates it, can significantly reduce the wavefront aberration of the illumination system, thereby greatly improving lithography resolution. Compared with traditional projection lithography illumination systems and holographic mask illumination systems based on spherical waves, the system can significantly reduce the number of lenses used, reduce the structural complexity of the illumination system, and thus reduce manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 Schematic diagram of the optical path of a plane wave-based illumination system according to an embodiment of the present invention;

[0048] Figure 2 Schematic diagram of the structure of a plane wave-based lighting system according to an embodiment of the present invention;

[0049] Figure 3 Schematic diagram of the optical path of the outgoing light of the plane wave-based illumination system according to an embodiment of the present invention;

[0050] Figure 4 is a schematic diagram of an optical modulation transfer function of a plane wave-based illumination system according to an embodiment of the present invention;

[0051] Figure 5 Schematic diagram of the root mean square wave aberration of the plane wave-based illumination system under a 0.00° field of view according to an embodiment of the present invention.

[0052] Description of reference numerals:

[0053] 1-first negative lens; 2-second negative lens; 3-third negative lens; 4-first meniscus lens; 5-second meniscus lens; 6-first positive lens. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the terms "front," "rear," "left," and "right," etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0057] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] Holographic lithography uses lasers to transfer patterns from a holographic mask onto substrates such as silicon wafers. Compared to projection lithography, holographic lithography has lower illumination system requirements and avoids the reliance on projection lenses common in conventional projection lithography. Plane wave-based illumination systems require the light output from the light source to be transmitted to the mask as a plane wave, placing high demands on alignment and aberration.

[0059] Specifically, in the field of holographic lithography, illumination systems are divided into spherical wave-based and plane wave-based systems. Spherical wave-based illumination systems require that the light output by the light source be propagated onto the reticle as a spherical wave, requiring a large numerical aperture to improve lithographic resolution. While spherical wave-based holographic illumination systems proposed in related art have significantly simplified their lens systems, they still require a large number of lenses and a relatively complex structure, requiring at least a dozen lenses. The tolerance sensitivity requirements are still high, and due to differences in their principles, they cannot yet meet the requirements for illuminating a holographic mask with a plane wave. Plane wave-based illumination systems, on the other hand, illuminate the reticle with a plane wave, eliminating the need for focusing the beam, but impose strict requirements on collimation and aberration. Currently, no illumination system suitable for plane wave holographic lithography has been proposed in the relevant field, and both conventional illumination systems and spherical wave illumination systems are extremely complex. Therefore, there is an urgent need for a simpler plane wave-based illumination system that meets the requirements of holographic lithography systems.

[0060] Therefore, in order to overcome at least one of the technical problems of the prior art illumination system, such as the complex structure and the inability to meet the requirements of plane wave holographic lithography, the embodiment of the present invention proposes an illumination system based on plane waves, see Figure 1 、 Figure 2 and Figure 3 .

[0061] The plane wave-based illumination system includes a first lens group and a second lens group arranged in sequence along the optical axis. The first lens group is used to expand the laser output by the light source. The second lens group is used to collimate the expanded laser and output the plane wave laser toward the holographic mask. The distance between the first lens group and the second lens group is the sum of the effective focal lengths of the first lens group and the second lens group.

[0062] Specifically, the first lens group and the second lens group are located between the light source and the holographic mask, and the first lens group has a total negative optical focal length so that the first lens group can expand the laser output by the light source. Exemplarily, the first lens group includes at least one negative lens. The negative lens will provide negative spherical aberration. In order to reduce the overall spherical aberration of the first lens group, multiple negative lenses can also be combined to jointly construct the first lens group. For example, the first lens group includes three negative lenses, which are arranged in sequence along the optical axis. By arranging a combination of three negative lenses, the aberration of the first lens group can be relatively reduced, and the structures of the three negative lenses are the same, which is convenient for processing. The negative lens will provide negative spherical aberration. In order to reduce the overall spherical aberration of the first lens group, the negative lens and the meniscus lens can also be combined to jointly construct the first lens group.

[0063] The second lens group has a total positive focal power, so that the second lens group can collimate the light beam, and the first lens group and the second lens group are in a confocal state, that is, the distance between the first lens group and the second lens group is the sum of the effective focal length of the first lens group and the effective focal length of the second lens group, so that the focus of the first lens group and the focus of the second lens group coincide, so that the outgoing light beam is parallel light, achieving high-precision collimation. Exemplarily, the second lens group includes a positive lens and a meniscus lens, or the second lens group includes two meniscus lenses, or the second lens group includes a positive lens and two meniscus lenses, etc. By adopting the form of a lens group, the wave aberration of the system can be reduced compared to single lens collimation. The positive lens will provide positive spherical aberration. In order to reduce the overall spherical aberration of the second lens group, the meniscus lens can be combined with the positive lens to jointly construct the second lens group. It is also possible to combine a number of meniscus lenses at intervals to construct the second lens group.

[0064] The lenses used in the first lens group and the second lens group can be made of ultraviolet fused silica or calcium fluoride to have good transmittance to ultraviolet light in the 193nm band.

[0065] The centers of the lenses used in the first lens group and the second lens group are all on the optical axis, and the relative positions between them are fixed by arranging mechanical components on the lens outer frames.

[0066] In the plane wave-based illumination system of the present invention, after the light beam emitted by the light source strikes the first lens group, the first lens group expands the beam. The second lens group then collimates the expanded laser light to produce collimated light. The beam propagates in the form of a plane wave toward the holographic mask, and then projects the image of the holographic mask onto the silicon wafer. By expanding the beam by the first lens group and then collimating it by the second lens group, the lens system significantly reduces wavefront aberrations in the illumination system, thereby greatly improving lithography resolution. Furthermore, compared to traditional projection lithography illumination systems and holographic mask illumination systems based on spherical waves, the system significantly reduces the number of lenses used, lowering the structural complexity of the illumination system and thus reducing manufacturing costs.

[0067] In some optional embodiments, the first lens group and the second lens group satisfy:

[0068]

[0069] Wherein, f′1 is the effective focal length of the first lens group, f2 is the effective focal length of the second lens group, and M is the magnification of the illumination system.

[0070] Specifically, the magnification M of the illumination system is a pre-set value. For holographic lithography illumination systems, the total system length has certain requirements. Therefore, the effective focal length of the second lens group should not be too large compared to the total system length. For example, the effective focal length of the second lens group can be f2 = 360 mm. When M is 30, the effective focal length of the first lens group is f′1 = 12 mm. By defining the relationship between the effective focal lengths of the first lens group and the second lens group using the magnification of the illumination system, the relationship between the effective focal lengths of the first and second lens groups can be determined when the magnification is determined, thereby facilitating the selection of lenses in the first and second lens groups to achieve the set magnification M.

[0071] In some optional embodiments, the first lens group includes a first negative lens 1, a second negative lens 2 and a third negative lens 3 arranged in sequence along the optical axis; the light-entry surface of the first negative lens 1 has a negative curvature radius, which is used to receive the laser output by the light source and perform a first beam expansion, and the light-exiting surface of the first negative lens 1 is a plane, which is used to maintain the light track of the laser beam expansion; the light-entry surface of the second negative lens 2 has a negative curvature radius, which is used to perform a second beam expansion on the laser incident through the first negative lens 1, and the light-exiting surface of the second negative lens 2 is a plane, which is used to maintain the light track of the laser beam expansion; the light-entry surface of the third negative lens 3 has a negative curvature radius, which is used to perform a third beam expansion on the laser incident through the second negative lens 2, and the light-exiting surface of the third negative lens 3 is a plane, which is used to maintain the light track of the laser beam expansion.

[0072] Specifically, the light-entry surfaces of the first negative lens 1, the second negative lens 2, and the third negative lens 3 are all concave surfaces with a negative radius of curvature, and the light-exiting surfaces are all planes with an infinite radius of curvature. Since the first negative lens 1, the second negative lens 2, and the third negative lens 3 all adopt a structure with a concave surface on one side and a plane on the other side, only the curvature radius of one side needs to be processed, and the other side only needs to be processed with a plane. The lens structure used is simple, which can simplify processing. In addition, the light-entry surface is a concave surface with a negative radius of curvature, which can be refracted and expanded, while the plane can maintain its expanded light trajectory. Through the first negative lens 1, the second negative lens 2, and the third negative lens 3, the laser can be expanded in the form of step-by-step progressive expansion of expansion-maintenance-expansion-maintenance-expansion-maintenance, ensuring the stability of the light beam during the expansion process and improving the expansion effect.

[0073] In some optional embodiments, the first negative lens 1, the second negative lens 2 and the third negative lens 3 satisfy the following conditions:

[0074] |r11|=|r21|=|r31|, and |r12|=|r22|=|r32|;

[0075] Among them, r11 and r12 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the first negative lens 1, r21 and r22 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the second negative lens 2, and r31 and r32 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the third negative lens 3.

[0076] Specifically, the light-entering surface, i.e., the front surface, of the first negative lens 1, the second negative lens 2, and the third negative lens 3 has a curvature radius of -25.6 mm, and the light-exiting surface, i.e., the rear surface, of the first negative lens 1, the second negative lens 2, and the third negative lens 3 is a plane. Since the curvature radius of the front surfaces of the first negative lens 1, the second negative lens 2, and the third negative lens 3 is the same, the curvature radius of the rear surfaces is also the same, which facilitates the production and processing of the first negative lens 1, the second negative lens 2, and the third negative lens 3.

[0077] In some optional embodiments, the lighting system further includes a compensation mechanism, which is connected to the third negative lens 3, and is used to drive the third negative lens 3 to move along the optical axis between the second negative lens 2 and the second lens group. The movement range Δl of the third negative lens 3 satisfies the following with reference to the starting position of the third negative lens 3: -1.0mm≤Δl≤+1.0mm.

[0078] During the photolithography process, the holographic mask will be replaced, and the thickness of each holographic mask may be different. Therefore, a compensation mechanism is added here to adjust the position of the third negative lens 3 on the optical axis, that is, the third negative lens 3 is driven to move along the front-to-back direction of the optical axis by the compensation mechanism, thereby compensating for the tolerance of the holographic mask thickness. The stroke of the compensation mechanism is ±1.0mm, and the accuracy is 2μm.

[0079] Furthermore, to achieve collimation, the first and second lens groups must be confocal, meaning they share the same focal point. However, during assembly, they may not be confocal due to assembly tolerances. In this case, a compensation mechanism can be used to drive the third negative lens 3 forward and backward along the optical axis to adjust the compensation.

[0080] Specifically, the compensation mechanism employs a mechanical translation fine-motion stage that carries the third negative lens 3, or a micromotor connected to the third negative lens 3 via an output shaft. The mechanical translation fine-motion stage or micromotor drives the third negative lens 3 to move along the optical axis to adjust the position of the third negative lens 3 on the optical axis, thereby compensating for tolerances in the thickness of the holographic mask or compensating for assembly tolerances.

[0081] In some optional embodiments, the distance D between the first negative lens 1 and the second negative lens 2 is 12 and the distance D between the second negative lens 2 and the third negative lens 3 23 Satisfied: D 12 <D 23 .

[0082] Specifically, the distance D between the first negative lens 1 and the second negative lens 2 is 12 Satisfies: 17mm<D 12 <18mm; the distance D between the second negative lens 2 and the third negative lens 3 23 Satisfies: 18mm<D 23 <19mm. Since the third negative lens 3 can be moved by the compensation mechanism, when D 12 <D 23 When the third negative lens 3 is moved, some space can be reserved for movement, and the system aberration can also be corrected.

[0083] In some optional embodiments, the effective focal length f1 of the first lens group is ′ satisfy:

[0084]

[0085] Among them, F1 ′ 2 is the combined focal length of the first negative lens 1 and the second negative lens 2, f1 ′3 is the effective focal length of the third negative lens 3, D 23 is the distance between the second negative lens 2 and the third negative lens 3; wherein the combined focal length F1 of the first negative lens 1 and the second negative lens 2 ′ 2 Satisfaction:

[0086]

[0087] Where f1 ′ 1 is the effective focal length of the first negative lens 1, f1 ′ 2 is the effective focal length of the second negative lens 2, D 12 is the distance between the first negative lens 1 and the second negative lens 2.

[0088] Specifically, the effective focal length of the first lens group is calculated by the combined focal length of the first negative lens 1 and the second negative lens 2, the effective focal length of the third negative lens 3, and the distance between the second negative lens 2 and the third negative lens 3, and then the combined focal length of the first negative lens 1 and the second negative lens 2 is calculated according to the effective focal length of the first negative lens 1, the effective focal length of the second negative lens 2, and the distance between the first negative lens 1 and the second negative lens 2. When the effective focal length of the first lens group is determined, the relationship between the effective focal lengths and the distances of the first negative lens 1, the second negative lens 2, and the third negative lens 3 can be obtained, so that the effective focal lengths and the distances of the first negative lens 1, the second negative lens 2, and the third negative lens 3 can be selected, so that the first lens group composed of the first negative lens 1, the second negative lens 2, and the third negative lens 3 can have a predetermined effective focal length.

[0089] In some optional embodiments, the effective focal length f1 of the first negative lens 1 is ′ 1. The effective focal length f1 of the second negative lens 2 ′ 2 and the effective focal length f1 of the third negative lens 3 ′ 3 Satisfaction:

[0090]

[0091]

[0092]

[0093] Among them, n is the refractive index of the lens material, r11 and r12 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the first negative lens 1 respectively, d11 is the thickness of the first negative lens 1, r21 and r22 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the second negative lens 2 respectively, d12 is the thickness of the second negative lens 2, r31 and r32 are the curvature radii of the light incident surface and the curvature radii of the light exit surface of the third negative lens 3 respectively, and d13 is the thickness of the third negative lens 3.

[0094] Specifically, the effective focal length is calculated by using the refractive index, lens thickness, the curvature radius of the light-entering surface, and the curvature radius of the light-exiting surface. When the effective focal length of the first negative lens 1, the second negative lens 2, or the third negative lens 3 is determined, parameters such as the lens thickness, the curvature radius of the light-entering surface, and the curvature radius of the light-exiting surface can be quickly selected, thereby making the design of the illumination system more reasonable, the preparation cost lower, and the system more suitable for the engineering realization of ultra-high-precision holographic lithography equipment.

[0095] In some optional embodiments, the second lens group includes a first meniscus lens 4, a second meniscus lens 5 and a first positive lens 6 arranged in sequence along the optical axis; the light entrance surface and the light exit surface of the first meniscus lens 4 both have a negative curvature radius, and the first meniscus lens 4 is used to perform a first collimation on the laser incident through the first lens group; the light entrance surface and the light exit surface of the second meniscus lens 5 both have a negative curvature radius, and the second meniscus lens 5 is used to perform a second collimation on the laser incident through the first meniscus lens 4; the light entrance surface and the light exit surface of the first positive lens 6 both have a negative curvature radius, and the first positive lens 6 is used to perform a third collimation on the laser incident through the second meniscus lens 5.

[0096] Specifically, the first meniscus lens 4 deflects the laser light incident through the first lens group toward parallel light, performing the initial collimation. The light-entering surface of the first meniscus lens 4 is a concave surface with a negative radius of curvature, which is used to collimate the expanded beam. The light-exiting surface of the first meniscus lens 4 is a convex surface with a negative radius of curvature, which receives the light exiting the light-entering surface and further collimates it.

[0097] The second meniscus lens 5 further collimates the laser light incident through the first meniscus lens 4, performing a secondary collimation. The light-entry surface of the second meniscus lens 5 is a concave surface with a negative radius of curvature, which further collimates the expanded beam. The light-exit surface of the second meniscus lens 5 is a convex surface with a negative radius of curvature, which receives the light exiting the light-entry surface and performs progressive collimation.

[0098] The first positive lens 6 performs the final collimation, or third collimation, of the laser beam incident through the second meniscus lens 5. The light-entry surface of the first positive lens 6 is a plane with an infinite radius of curvature, which receives the output beam from the second meniscus lens 5 and maintains its collimation. The light-exit surface of the first positive lens 6 is a convex surface with a negative radius of curvature, which receives the output light from the light-entry surface and further collimates it.

[0099] Progressive collimation is achieved by the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6, with good collimation effect. Moreover, the first meniscus lens 4 and the second meniscus lens 5 both have a concave and a convex structure, which can effectively reduce the spherical aberration of the system.

[0100] In some optional embodiments, the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 satisfy the following conditions:

[0101] |r61|>|r51|>|r41|, and |r62|>|r52|>|r42|;

[0102] Among them, r41 and r42 are the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first meniscus lens 4, r51 and r52 are the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the second meniscus lens 5, r61 and r62 are the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens 6, respectively.

[0103] Specifically, the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first meniscus lens 4 are -234.84 mm and -145.45 mm respectively, the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the second meniscus lens 5 are -617.31 mm and -257.86 mm respectively, the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens 6 are infinity and -413.17 mm respectively. Since |r61|>|r51|>|r41|, and |r62|>|r52|>|r42|, the refractive effects of the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 on the light beam decrease in sequence. By using the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 whose refractive effects decrease in sequence, the collimation effect of the laser can be improved.

[0104] In some optional embodiments, the distance D between the first meniscus lens 4 and the second meniscus lens 5 is 45 Satisfies: 15mm<D 45 <16mm; the distance D between the second meniscus lens 5 and the first positive lens 6 56 Satisfies: 15mm<D 56 <16mm.

[0105] Specifically, the distance D between the first meniscus lens 4 and the second meniscus lens 5 is 45 The distance D between the second meniscus lens 5 and the first positive lens 6 is 15.5 mm. 56 15.5mm, D 45 and D 56 The propagation distances of the light beams after being collimated by the first meniscus lens 4 and the second meniscus lens 5 are approximately equal, which can improve the collimation effect of the second lens group.

[0106] In some optional embodiments, the effective focal length f2 of the second lens group satisfies:

[0107]

[0108] Among them, F4 ′ 5 is the combined focal length of the first meniscus lens 4 and the second meniscus lens 5, f2 ′ 3 is the effective focal length of the first positive lens 6, D 56 is the distance between the second meniscus lens 5 and the first positive lens 6;

[0109] The combined focal length F4 of the first meniscus lens 4 and the second meniscus lens 5 ′ 5 Satisfaction:

[0110]

[0111] Among them, f2 ′ 1 is the effective focal length of the first meniscus lens 4, f2 ′ 2 is the effective focal length of the second meniscus lens 5, D 45 is the distance between the first meniscus lens 4 and the second meniscus lens 5.

[0112] Specifically, the effective focal length of the second lens group is calculated by the combined focal length of the first meniscus lens 4 and the second meniscus lens 5, the effective focal length of the first positive lens 6, and the distance between the second meniscus lens 5 and the first positive lens 6, and then the combined focal length of the first meniscus lens 4 and the second meniscus lens 5 is calculated according to the effective focal length of the first meniscus lens 4, the effective focal length of the second meniscus lens 5, and the distance between the first meniscus lens 4 and the second meniscus lens 5. When the effective focal length of the second lens group is determined, the relationship between the effective focal lengths and the distances of the first meniscus lens 4, the second meniscus lens 5, and the first positive lens 6 can be obtained, so that the effective focal lengths and the distances of the first meniscus lens 4, the second meniscus lens 5, and the first positive lens 6 can be selected, so that the second lens group composed of the first meniscus lens 4, the second meniscus lens 5, and the first positive lens 6 can have a predetermined effective focal length.

[0113] In some optional embodiments, the effective focal length f2 of the first meniscus lens 4 is ′ 1. The effective focal length f2 of the second meniscus lens 5 ′ 2 and the effective focal length f2 of the first positive lens 6 ′ 3 Satisfaction:

[0114]

[0115]

[0116]

[0117] Among them, r41 and r42 are the curvature radii of the light incident surface and the curvature radii of the light emitting surface of the first meniscus lens 4 respectively, d21 is the thickness of the first meniscus lens 4, r51 and r52 are the curvature radii of the light incident surface and the curvature radii of the light emitting surface of the second meniscus lens 5 respectively, d22 is the thickness of the second meniscus lens 5, r61 and r62 are the curvature radii of the light incident surface and the curvature radii of the light emitting surface of the first positive lens 6 respectively, and d23 is the thickness of the first positive lens 6.

[0118] Specifically, the effective focal length is calculated by the refractive index, lens thickness, curvature radius of the light-entering surface, and curvature radius of the light-exiting surface. When the effective focal lengths of the first meniscus lens 4, the second meniscus lens 5, and the first positive lens 6 are determined, parameters such as the lens thickness, curvature radius of the light-entering surface, and curvature radius of the light-exiting surface can be quickly selected, thereby making the design of the lighting system more reasonable.

[0119] In some optional embodiments, an aperture is provided between the first lens group and the second lens group, and the distance between the aperture and the first lens group is greater than the distance between the aperture and the second lens group.

[0120] Specifically, the distance between the aperture and the first lens group is 143mm-144mm, and the distance between the aperture and the second lens group is 21mm-22mm. The aperture is used to limit the range of the light beam. Since the distance between the aperture and the first lens group is greater than the distance between the aperture and the second lens group, the aperture is closer to the second lens group, which can reduce the scattered light of the light beam.

[0121] In some optional embodiments, the first negative lens 1 , the second negative lens 2 , the third negative lens 3 , the first meniscus lens 4 , the second meniscus lens 5 and the first positive lens 6 are all spherical lenses.

[0122] Specifically, a combination of a first negative lens 1, a second negative lens 2, a third negative lens 3, a first meniscus lens 4, a second meniscus lens 5 and a first positive lens 6 is selected to generate a plane wave. Even if a spherical mirror is used, the overall spherical aberration is still small, and the lens does not need to use aspherical mirrors, cemented mirrors and other lenses that reduce spherical aberration. Compared with aspherical mirrors and cemented mirrors, spherical mirrors have a simple structure and are easy to process.

[0123] The working principle of the plane wave-based lighting system of the embodiment of the present invention is as follows:

[0124] The laser light emitted by the light source is incident on the first negative lens 1, refracted by the first lens group to achieve beam expansion, and then refracted and collimated into a plane wave by the second lens group. The first lens group serves as a beam expander, while the second lens group serves as a collimator. The first negative lens 1, the second negative lens 2, and the third negative lens 3 have the same radius of curvature. Combining them together can expand the laser beam to a certain spot diameter. The second lens group uses a combination of a first meniscus lens 4, a second meniscus lens 5, and a first positive lens 6 to collimate the expanded beam and reduce the wavefront aberration of the entire illumination system.

[0125] The embodiment of the present invention uses two evaluation methods to evaluate the plane wave-based lighting system.

[0126] Specifically, in the plane wave-based illumination system, the first lens group includes a first negative lens 1, a second negative lens 2, and a third negative lens 3, which are sequentially arranged along the optical axis. The second lens group includes a first meniscus lens 4, a second meniscus lens 5, and a first positive lens 6. The first negative lens 1, the second negative lens 2, the third negative lens 3, the first meniscus lens 4, the second meniscus lens 5, and the first positive lens 6 are all made of ultraviolet fused silica and are spherical mirrors. The holographic illumination system operates in a nitrogen-filled environment. The refractive index of ultraviolet fused silica under nitrogen is 1.560737. The light source is a 193nm ArF laser. By optimizing the various lenses of the plane wave-based illumination system, the curvature radius, thickness, and spacing of the various lenses of the plane wave-based illumination system are shown in the following table:

[0127]

[0128]

[0129] In the table above, STO represents the aperture, and its corresponding spacing represents the distance between the aperture and first meniscus lens 4. The distances corresponding to the remaining surfaces represent the mid-range thickness of each lens and the distance between two adjacent lenses in the order of first negative lens 1, second negative lens 2, third negative lens 3, first meniscus lens 4, second meniscus lens 5, and first positive lens 6. The specific parameters of these lenses can be fine-tuned during actual operation to meet different system parameter requirements.

[0130] Specifically, in the plane wave-based illumination system evaluated in this study, the first negative lens 1 has a light-entry surface with a curvature radius of -25.6 mm, a flat light-exit surface, and a thickness of 16.5 mm. The distance between the first negative lens 1 and the second negative lens 2 is 17.5 mm.

[0131] The curvature radius of the light incident surface of the second negative lens 2 is -25.6 mm, the light emitting surface is flat, the thickness is 14.5 mm, and the distance between the second negative lens 2 and the third negative lens 3 is 18.5 mm;

[0132] The third negative lens 3 has a light entrance surface with a curvature radius of -25.6 mm, a flat light exit surface, a thickness of 16.5 mm, and a distance from the aperture to the lens of 143.5 mm.

[0133] The first meniscus lens 4 has a light-entry surface with a curvature radius of -234.84 mm, a light-exit surface with a curvature radius of -145.45 mm, a thickness of 21.5 mm, and a distance from the aperture of 21.5 mm and from the second meniscus lens 5 of 15.6 mm.

[0134] The curvature radius of the light-entry surface of the second meniscus lens 5 is -617.31 mm, the curvature radius of the light-exit surface is -257.86 mm, the thickness is 20.5 mm, and the distance between the second meniscus lens 5 and the first positive lens 6 is 15.5 mm;

[0135] The light incident surface of the first positive lens 6 is a plane, the curvature radius of the light emitting surface is -413.17 mm, the thickness is 19.5 mm, and the distance from the holographic mask is 50.5 mm.

[0136] The evaluation results of the above-mentioned plane wave-based lighting system using two evaluation methods are as follows:

[0137] 1. Optical Modulation Transfer Function (MTF) Evaluation

[0138] The optical modulation transfer function is a direct evaluation of the resolution of the optical system. Figure 4 As shown, the optical modulation transfer function (OTF is the optical transfer function, and the modulus of the optical transfer function OTF is the MTF) obtained by the optical software Zemax shows that in the embodiment of the present invention, the MTF of the plane wave-based illumination system has basically reached the diffraction limit.

[0139] 2. Root mean square wave aberration evaluation

[0140] See Figure 5The RMS wavefront aberration is shown using a wavelength λ equal to 193.368 nm. For the plane wave-based illumination system according to the present invention, with the central ray as the reference, i.e., at a 0.00° field of view, the minimum RMS wavefront aberration is 0.0013λ, or 0.25nm. The plane wave-based illumination system according to the present invention has relatively low RMS wavefront aberration values. Reducing wavefront aberration can improve lithography resolution, and therefore, the present invention can improve lithography resolution.

[0141] The plane wave-based lighting system in the embodiment of the present invention has the following advantages:

[0142] 1. The plane wave-based illumination system consists of only six lenses, without the use of aspheric mirrors or any cemented mirrors. The simple and compact structure simplifies the manufacturing process and reduces manufacturing costs. Compared with existing technologies, it has a higher tolerance for manufacturing and assembly tolerances.

[0143] 2. The operating wavelength of the holographic illumination system is 193nm, and the root mean square wave aberration referenced to the central light is less than 0.05λ, so it has a high lithography resolution.

[0144] 3. Compensation adjustment of the thickness tolerance and assembly tolerance of the holographic mask can be achieved through a compensation mechanism, and the structure is simple.

[0145] 4. Expand the beam - hold - expand the beam - hold - expand the beam - hold. This step-by-step progressive expansion method ensures the stability of the beam during the expansion process and greatly improves the stable expansion effect.

[0146] 5. Progressive collimation is achieved through the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6, resulting in a better collimation effect.

[0147] In summary, the plane wave-based illumination system in the embodiment of the present invention improves the system integration and reduces the cost of the lithography process compared with traditional lithography technology. It also has extremely high lithography resolution, meets the requirements of ultra-high precision holographic lithography, and can greatly ensure the exposure yield during the lithography process.

[0148] An embodiment of the present invention further provides an exposure device for use in a chip fabrication process, wherein the exposure device is used to perform an exposure process on a silicon wafer. The exposure device includes the plane wave-based illumination system of the above embodiment. The specific implementation and beneficial effects of the exposure device can be found in the plane wave-based illumination system of the above embodiment and are not further described here.

[0149] Although the embodiments of the present invention are described above with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A plane wave based illumination system for holographic lithography, characterized in that: include: A first lens group and a second lens group are sequentially arranged along the optical axis; The first lens group is used to expand the laser beam output by the light source; The second lens group is used to collimate the expanded laser beam and output a plane wave laser beam toward the holographic mask. The distance between the first lens group and the second lens group is the sum of the effective focal length of the first lens group and the effective focal length of the second lens group; The first lens group comprises a first negative lens (1), a second negative lens (2) and a third negative lens (3) which are sequentially arranged along the optical axis direction; The light-entry surface of the first negative lens (1) has a negative curvature radius and is used to receive the laser output by the light source and perform a first beam expansion. The light-exit surface of the first negative lens (1) is a plane and is used to maintain the light trace of the laser beam expansion. The light-entry surface of the second negative lens (2) has a negative curvature radius, and is used to perform a second beam expansion on the laser incident through the first negative lens (1); the light-exit surface of the second negative lens (2) is a plane, and is used to maintain the light trace of the laser beam expansion; The light-entry surface of the third negative lens (3) has a negative curvature radius, and is used to perform a third beam expansion on the laser incident through the second negative lens (2); the light-exit surface of the third negative lens (3) is a plane, and is used to maintain the light trace of the laser beam expansion; The second lens group comprises a first meniscus lens (4), a second meniscus lens (5) and a first positive lens (6) which are sequentially arranged along the optical axis direction; The light-entry surface and the light-exiting surface of the first meniscus lens (4) both have a negative curvature radius, and the first meniscus lens (4) is used to perform a first collimation on the laser incident through the first lens group; The light-entry surface and the light-exiting surface of the second meniscus lens (5) both have a negative curvature radius, and the second meniscus lens (5) is used to perform a second collimation on the laser light incident through the first meniscus lens (4); The light-entry surface of the first positive lens (6) is a plane with an infinite curvature radius, and the light-exit surface has a negative curvature radius. The first positive lens (6) is used to perform a third collimation on the laser incident through the second meniscus lens (5); the first lens group and the second lens group satisfy: Wherein, f′1 is the effective focal length of the first lens group, f2 is the effective focal length of the second lens group, and M is the magnification of the illumination system; The first negative lens (1), the second negative lens (2) and the third negative lens (3) satisfy the following conditions: |r11|=|r21|=|r31|, and |r12|=|r22|=|r32|; wherein r11 and r12 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the first negative lens (1); r21 and r22 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the second negative lens (2); and r31 and r32 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the third negative lens (3); The distance D between the first negative lens (1) and the second negative lens (2) is 12 and the distance D between the second negative lens (2) and the third negative lens (3) 23 Satisfied: D 12 <D 23 ; The effective focal length f′1 of the first lens group satisfies: Among them, F′ 12 is the combined focal length of the first negative lens (1) and the second negative lens (2), f′ 13 is the effective focal length of the third negative lens (3), D 23 is the distance between the second negative lens (2) and the third negative lens (3); The combined focal length F′ of the first negative lens (1) and the second negative lens (2) is 12 satisfy: Where f′ 11 is the effective focal length of the first negative lens (1), f′ 12 is the effective focal length of the second negative lens (2), D 12 is the distance between the first negative lens (1) and the second negative lens (2); The effective focal length f' of the first negative lens (1) 11 , the effective focal length f′ of the second negative lens (2) 12 and the effective focal length f′ of the third negative lens (3) 13 satisfy: wherein n is the refractive index of the lens material, r11 and r12 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the first negative lens (1), d11 is the thickness of the first negative lens (1), r21 and r22 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the second negative lens (2), d12 is the thickness of the second negative lens (2), r31 and r32 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-exiting surface of the third negative lens (3), and d13 is the thickness of the third negative lens (3); The first meniscus lens (4), the second meniscus lens (5) and the first positive lens (6) satisfy the following conditions: |r61|>|r51|>|r41|, and |r62|>|r52|>|r42|; wherein r41 and r42 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the first meniscus lens (4); r51 and r52 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the second meniscus lens (5); and r61 and r62 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the first positive lens (6); The distance D between the first meniscus lens (4) and the second meniscus lens (5) is 45 Satisfies: 15mm<D 45 <16mm; The distance D between the second meniscus lens (5) and the first positive lens (6) is 56 Satisfies: 15mm<D 56 <16mm; The effective focal length f2 of the second lens group satisfies: Among them, F′ 45 is the combined focal length of the first meniscus lens (4) and the second meniscus lens (5), f′ 23 is the effective focal length of the first positive lens (6), D 56 is the distance between the second meniscus lens (5) and the first positive lens (6); The combined focal length F′ of the first meniscus lens (4) and the second meniscus lens (5) 45 satisfy: Among them, f′ 21 is the effective focal length of the first meniscus lens (4), f′ 22 is the effective focal length of the second meniscus lens (5), D 45 is the distance between the first meniscus lens (4) and the second meniscus lens (5); The effective focal length f' of the first meniscus lens (4) 21 , the effective focal length f′ of the second meniscus lens (5) 22 and the effective focal length f′ of the first positive lens (6) 23 satisfy: wherein r41 and r42 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the first meniscus lens (4), d21 is the thickness of the first meniscus lens (4), r51 and r52 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the second meniscus lens (5), d22 is the thickness of the second meniscus lens (5), r61 and r62 are respectively the curvature radii of the light-entering surface and the curvature radii of the light-emitting surface of the first positive lens (6), and d23 is the thickness of the first positive lens (6); the first negative lens (1), The second negative lens (2), the third negative lens (3), the first meniscus lens (4), the second meniscus lens (5) and the first positive lens (6) all adopt spherical mirrors; the lighting system further comprises a compensation mechanism, the compensation mechanism is connected to the third negative lens (3), the compensation mechanism is used to drive the third negative lens (3) to move along the optical axis between the second negative lens (2) and the second lens group, and the moving range Δl of the third negative lens (3) satisfies the following with reference to the starting position of the third negative lens (3): -1.0mm≤Δl≤+1.0mm.

2. The plane wave based lighting system according to claim 1, wherein: An aperture is provided between the first lens group and the second lens group, and a distance between the aperture and the first lens group is greater than a distance between the aperture and the second lens group.

3. An exposure device, used in chip preparation process, characterized by: The invention comprises a plane wave based illumination system as claimed in any one of claims 1 to 2.

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