Illumination system based on plane waves and exposure equipment

Abstract

The invention relates to the technical field of holographic lithography systems, and discloses a plane wave-based illumination system and exposure equipment, and the plane wave-based illumination system comprises a first lens group and a second lens group which are sequentially arranged along an optical axis direction; the first lens group is used for expanding the laser output by the light source; the second lens group is used for collimating the expanded laser and outputting plane wave laser to the direction of 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 light beam is expanded by the first lens group, then the light beam is collimated by the second lens group, and the wave aberration of the illumination system can be reduced by adopting the form of the lens group, so that the photoetching resolution is improved; and compared with a traditional projection photoetching illumination system and a holographic mask illumination system based on spherical waves, the number of used lenses can be reduced, and the manufacturing cost is reduced.

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 the large-scale integrated circuit manufacturing process, the photolithography device is an extremely important device. It is a technology that uses lasers to image mask patterns onto silicon wafers. In the field of traditional projection lithography, the projection lithography objective lens with an operating wavelength of 193nm is the core component of the projection lithography device for making ultra-fine patterns.

[0003] In the field of traditional projection lithography, the projection lithography objective lens with an operating wavelength of 193nm is the core component of the projection lithography device for producing ultra-fine patterns. However, these objective lenses have complex structures, and most of them have advanced aspheric surfaces. The system volume is large, and the requirements for the manufacturing integrated assembly process are high. For example, patent US20030030916A1 introduces a projection lithography objective lens with a maximum numerical aperture of 0.89, including at least 4 groups of lenses, a total of 29 lenses, each group of lenses has either positive or negative focal power, and multiple lens groups are required to expand and focus the light beam multiple times. Therefore, low-cost, highly integrated new lithography technology will promote the development of lithography and semiconductor fields.

[0004] Holographic lithography systems can be used in the manufacture of integrated circuits. It is a technology that uses lasers to image holographic mask patterns onto substrates such as silicon wafers. Compared with projection lithography, holographic lithography has lower requirements for the lighting system process. There is no object-image relationship between the mask and the silicon wafer, which can avoid the reliance of conventional projection lithography on projection lenses. In the holographic lithography system, the performance of the holographic illumination system is the key to holographic lithography technology, which directly determines the graphic transmission capability of the entire exposure device. Summary of the invention

[0005] In view of this, the present invention provides a plane wave-based illumination system and exposure equipment, 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 which are arranged in sequence along the optical axis; the light entrance 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 entrance surface of the second negative lens has a negative curvature radius, which is used to perform the second beam expansion of 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 entrance surface of the third negative lens has a negative curvature radius, which is used to perform the third beam expansion of 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 Satisfaction: 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 incident 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 incident 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 incident 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 which are 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 emitting 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 emitting 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 emitting surface of the first positive lens respectively.

[0029] Optionally, the distance D between the first meniscus lens and the second meniscus lens is 45 Satisfy: 15mm<D 45 <16mm; the distance D between the second meniscus lens and the first positive lens 56 Satisfy: 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 respectively the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first meniscus lens, d21 is the thickness of the first meniscus lens, r51 and r52 are respectively the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the second meniscus lens, d22 is the thickness of the second meniscus lens, r61 and r62 are respectively the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens, 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, and a moving range Δl of the third negative lens satisfies the following with reference to a starting position of the third negative lens: -1.0mm≤Δl≤+1.0mm.

[0042] Optionally, an aperture stop is provided between the first lens group and the second lens group, and a distance between the aperture stop and the first lens group is greater than a distance between the aperture stop 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 device 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 irradiates the first lens group, the first lens group expands the light beam, and the expanded laser is collimated by the second lens group to obtain collimated light. The light beam propagates in the direction of the holographic mask in the form of a plane wave, and then the image of the holographic mask is projected onto the silicon wafer. The light beam is expanded by the first lens group, and then collimated by the second lens group. The light beam is expanded first and then collimated in the form of a lens group, which can significantly reduce the wave aberration of the illumination system, thereby greatly improving the lithography resolution, and compared with the illumination system of the traditional projection lithography and the holographic mask illumination system based on the spherical wave, the number of lenses used can be greatly reduced, and the structural complexity of the illumination system can be reduced, thereby reducing the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0048] Figure 2 is a schematic structural diagram 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 described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "front", "rear", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0056] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to 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 system is a technology that uses laser to image the pattern on the holographic mask onto a substrate such as a silicon wafer. Compared with projection lithography, holographic lithography has lower requirements on the process of the illumination system and can avoid the dependence of conventional projection lithography on the projection objective. The illumination system based on plane waves needs to propagate the light output by the light source to the mask in the form of plane waves, which has high requirements on the collimation effect and aberration.

[0059] Specifically, in the field of holographic lithography, its illumination system is divided into an illumination system based on spherical waves and an illumination system based on plane waves. Among them, the illumination system based on spherical waves needs to propagate the light output by the light source to the mask in the form of spherical waves, requiring the illumination system to have a large numerical aperture to improve the lithography resolution. The holographic illumination system based on spherical waves proposed in the related art has achieved lens simplification to a great extent, but the number of lenses is still large, the structure is still relatively complex, and at least a dozen lenses are required. The tolerance sensitivity requirement is still high, and due to the difference in principles, it cannot meet the requirements of irradiating the holographic mask through a plane wave. The illumination system based on plane waves needs to illuminate the mask through a plane wave, and does not need to focus the light beam, but has high requirements for the collimation effect and aberration. At present, the related field has not yet proposed an illumination system suitable for plane wave holographic lithography, and the structures of traditional illumination systems or spherical wave illumination systems are extremely complex. Therefore, there is an urgent need for an illumination system based on plane waves with a simpler structure to meet the requirements of the holographic lithography system.

[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 comprises a first lens group and a second lens group sequentially arranged along an optical axis direction; the first lens group is used for expanding the laser light outputted by a light source; the second lens group is used for collimating the expanded laser light and outputting the plane wave laser light 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.

[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 coincides with the focus of the second lens group, so that the emitted light beam is parallel light, and high-precision collimation is achieved. 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 may be made of ultraviolet fused quartz or calcium fluoride to have better 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 irradiates the first lens group, the first lens group expands the light beam, and the expanded laser is collimated by the second lens group to obtain collimated light. The light beam propagates in the direction of the holographic mask in the form of a plane wave, and then the image of the holographic mask is projected onto the silicon wafer. The light beam is expanded by the first lens group, and then collimated by the second lens group. The light beam is expanded first and then collimated in the form of a lens group, which can significantly reduce the wave aberration of the illumination system, thereby greatly improving the lithography resolution; and compared with the illumination system of the traditional projection lithography and the holographic mask illumination system based on the spherical wave, the number of lenses used can be greatly reduced, and the structural complexity of the illumination system can be reduced, thereby reducing the manufacturing cost.

[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 preset value. For the illumination system of holographic lithography, the total length of the system has certain requirements, so the effective focal length of the second lens group should not be too large compared with the total length of the system. For example, the effective focal length of the second lens group can be f2=360mm. When M is 30, the effective focal length of the first lens group is f′1=12mm. The relationship between the effective focal length of the first lens group and the effective focal length of the second lens group is limited by the magnification of the illumination system. When the magnification is determined, the relationship between the effective focal lengths of the first lens group and the second lens group can be obtained, thereby facilitating the selection of lenses in the first lens group and the second lens group to obtain 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 entrance 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 exit 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 entrance 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 exit 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 entrance 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 exit 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-entering surfaces of the first negative lens 1, the second negative lens 2, and the third negative lens 3 are all concave surfaces with negative radius of curvature, and the light-emitting surfaces are all planes with 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 in which one side is concave and the other side is plane, only the radius of curvature of one side needs to be processed, and only the plane needs to be processed on the other side. The lens structure used is simple and the processing can be simplified. In addition, the light-entering 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 trace. 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 expansion-maintenance-expansion-maintenance-expansion-maintenance, a step-by-step progressive expansion, which ensures the stability of the light beam during the expansion process and improves the expansion effect.

[0073] In some optional implementations, 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 emitting 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 emitting surface 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 emitting surface of the third negative lens 3, respectively.

[0076] Specifically, the light incident 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 exit 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 front surfaces of the first negative lens 1, the second negative lens 2, and the third negative lens 3 have the same curvature radius and the rear surfaces have the same curvature radius, the production and processing of the first negative lens 1, the second negative lens 2, and the third negative lens 3 are facilitated.

[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, and a 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.

[0078] When performing 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 and rear directions of the optical axis by the compensation mechanism, so as to compensate for the tolerance of the thickness of the holographic mask. The stroke of the compensation mechanism is ±1.0mm, and the accuracy is 2μm.

[0079] In addition, in order to achieve collimation, the first lens group and the second lens group must be in a confocal state, that is, they have the same focus. However, in the assembly state, they may not be confocal due to assembly tolerance. In this case, the compensation mechanism can also be used to drive the third negative lens 3 to move along the front-rear direction of the optical axis to adjust the compensation.

[0080] Specifically, the compensation mechanism adopts a mechanical translation micro-motion stage carrying the third negative lens 3, or a micro-motor connected to the third negative lens 3 via an output shaft. The third negative lens 3 is driven to move along the optical axis by the mechanical translation micro-motion stage or the micro-motor to adjust the position of the third negative lens 3 on the optical axis, thereby compensating for the tolerance of the thickness of the holographic mask or compensating for the assembly tolerance.

[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 Satisfaction: D 12 <D 23 .

[0082] Specifically, the distance D between the first negative lens 1 and the second negative lens 2 is 12 Satisfy: 17mm<D 12 <18mm; the distance D between the second negative lens 2 and the third negative lens 3 23 Satisfy: 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, and the system aberration can also be corrected.

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

[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 between 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 between 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 exiting 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 exiting 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 exiting 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 the refractive index, lens thickness, the radius of curvature of the light-incoming surface and the radius of curvature 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 radius of curvature of the light-incoming surface and the radius of curvature of the light-exiting surface can be quickly selected, thereby making the design of the illumination system more reasonable, the preparation cost lower, and 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, which are 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 the parallel light direction, i.e., the first collimation. The light-entering surface of the first meniscus lens 4 is a concave surface with a negative curvature radius, which is used to collimate the light beam after expansion. The light-exiting surface of the first meniscus lens 4 is a convex surface with a negative curvature radius, which is used to receive the outgoing light from the light-entering surface and further collimate it.

[0097] The second meniscus lens 5 further collimates the laser light incident through the first meniscus lens 4, i.e., performs the second collimation. The light-entering surface of the second meniscus lens 5 is a concave surface with a negative curvature radius, which is used to further collimate the beam after expansion. The light-exiting surface of the second meniscus lens 5 is a convex surface with a negative curvature radius, which is used to receive the exiting light from the light-entering surface and perform progressive collimation on it.

[0098] The first positive lens 6 performs the final collimation, i.e., the third collimation, on the laser beam incident through the second meniscus lens 5. The light-entering surface of the first positive lens 6 is a plane with an infinite radius of curvature, which is used to receive the outgoing light beam from the second meniscus lens 5 and maintain its collimated light beam. The light-exiting surface of the first positive lens 6 is a convex surface with a negative radius of curvature, which is used to receive the outgoing light from the light-entering surface and further collimate it.

[0099] Progressive collimation is achieved by the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6, and the collimation effect is good. In addition, 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 implementations, 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.

[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 refraction effects of the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 on the light beam decrease successively. By using the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 whose refraction effects decrease successively, 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 Satisfy: 15mm<D 45 <16mm; the distance D between the second meniscus lens 5 and the first positive lens 6 56 Satisfy: 15mm<D 56 <16mm.

[0105] Specifically, the distance D between the first meniscus lens 4 and the second meniscus lens 5 is 45 is 15.5 mm, and the distance D between the second meniscus lens 5 and the first positive lens 6 is 56 15.5mm, D 45 and D 56 The distances of the light beams collimated by the first meniscus lens 4 and the second meniscus lens 5 are equal or approximately equal, that is, the propagation distances of the light beams 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 respectively the curvature radius of the light incident surface and the curvature radius 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 radius of the light incident surface and the curvature radius 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 radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens 6, 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, the radius of curvature of the light incident surface and the radius of curvature 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, the radius of curvature of the light incident surface and the radius of curvature 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 stop is provided between the first lens group and the second lens group, and a distance between the aperture stop and the first lens group is greater than a distance between the aperture stop and the second lens group.

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

[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 an aspherical mirror, a cemented mirror or other lens that reduces spherical aberration. Compared with an aspherical mirror and a cemented mirror, a spherical mirror has a simple structure and is easy to process.

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

[0124] The laser emitted by the light source is incident from the first negative lens 1, refracted by the first lens group to complete the beam expansion, and then refracted by the second lens group to collimate it into a plane wave. The first lens group plays a role in beam expansion, and the second lens group plays a role in collimation. The first negative lens 1, the second negative lens 2 and the third negative lens 3 have the same radius of curvature, and combining them together can expand the laser beam to a certain spot diameter. The second lens group uses a combination of the first meniscus lens 4, the second meniscus lens 5 and the first positive lens 6 in order to collimate the expanded beam and reduce the wave aberration of the entire lighting 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 arranged in sequence along the optical axis, and 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 quartz and are spherical mirrors. The holographic illumination system works in a nitrogen-filled environment. The refractive index of ultraviolet fused quartz under nitrogen is 1.560737. The light source is a 193nm ArF laser. By optimizing each lens of the plane wave-based illumination system, the curvature radius, thickness, and spacing of each lens of the plane wave-based illumination system are obtained as shown in the following table:

[0127]

[0128]

[0129] In the above table, STO represents the aperture, and its corresponding spacing represents the distance between the aperture and the first meniscus lens 4. The distances corresponding to the other surfaces represent the middle thickness of each lens and the distance between two adjacent lenses in 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, which are arranged in sequence. The specific parameters of the above lenses can be fine-tuned accordingly to meet different system parameter requirements during actual operation.

[0130] Specifically, in the plane wave-based illumination system evaluated in this study, the radius of curvature of the light-entering surface of the first negative lens 1 is -25.6 mm, the light-exiting surface is a plane, the thickness is 16.5 mm, and the distance between it and the second negative lens 2 is 17.5 mm;

[0131] The curvature radius of the light-entering surface of the second negative lens 2 is -25.6 mm, the light-exiting surface is a plane, 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 curvature radius of the light entrance surface of the third negative lens 3 is -25.6 mm, the light exit surface is a plane, the thickness is 16.5 mm, and the distance between the third negative lens 3 and the aperture is 143.5 mm;

[0133] The first meniscus lens 4 has a curvature radius of -234.84 mm on the light-entering surface, a curvature radius of -145.45 mm on the light-exiting surface, a thickness of 21.5 mm, a distance between the first meniscus lens 4 and the aperture of 21.5 mm, and a distance between the first meniscus lens 4 and the second meniscus lens 5 of 15.6 mm;

[0134] The curvature radius of the light-entering surface of the second meniscus lens 5 is -617.31 mm, the curvature radius of the light-exiting surface is -257.86 mm, the thickness is 20.5 mm, and the distance from 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 plane wave-based lighting system by 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. RMS wavefront aberration evaluation

[0140] See also Figure 5, the root mean square wave aberration is displayed with the wavelength λ equal to 193.368nm as the unit. The plane wave-based illumination system of the embodiment of the present invention takes the central light as the reference, that is, at a 0.00° field of view, the minimum value of the root mean square wave aberration of the system is 0.0013λ, that is, 0.25nm. The root mean square wave aberration values ​​of the plane wave-based illumination system of the embodiment of the present invention are all relatively low. The reduction of wave aberration can improve the lithography resolution, so the embodiment of the present invention can improve the 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 6 lenses, does not use aspheric mirrors, and does not have a single glued mirror. It has a simple and compact structure, which simplifies the manufacturing process and reduces the manufacturing cost. Compared with the existing technology, it has a high 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 higher 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, and the collimation effect is better.

[0147] In summary, compared with traditional lithography technology, 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, and 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] The embodiment of the present invention further provides an exposure device, which is applied to a chip preparation process, and the exposure process is performed on a silicon wafer by the exposure device, and the exposure device includes the plane wave-based illumination system in the above embodiment. The specific implementation and beneficial effects of the exposure device can be referred to the plane wave-based illumination system in the above embodiment, and will not be described in detail here.

[0149] Although the embodiments of the present invention are described above in conjunction with the 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 are all 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 direction; 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 and output the plane wave laser in the direction of 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.

2. The plane wave based lighting system according to claim 1, characterized in that: The first lens group and the second lens group satisfy: 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.

3. The plane wave based lighting system according to claim 1, characterized in that: The first lens group comprises a first negative lens (1), a second negative lens (2) and a third negative lens (3) which are arranged in sequence along the optical axis direction; The light-incoming surface of the first negative lens (1) has a negative curvature radius and is used to receive the laser light output by the light source and perform a first beam expansion. The light-outgoing surface of the first negative lens (1) is a plane and is used to maintain the light track of the laser beam expansion. The light-incoming surface of the second negative lens (2) has a negative curvature radius, and is used to perform a second beam expansion on the laser beam incident through the first negative lens (1); the light-outgoing 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-incoming 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-outgoing surface of the third negative lens (3) is a plane, and is used to maintain the light trace of the laser beam expansion.

4. The plane wave based lighting system according to claim 3, characterized in that: 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|; Among them, r11 and r12 are respectively the curvature radius of the light entrance surface and the curvature radius of the light exit surface of the first negative lens (1), r21 and r22 are respectively the curvature radius of the light entrance surface and the curvature radius of the light exit surface of the second negative lens (2), and r31 and r32 are respectively the curvature radius of the light entrance surface and the curvature radius of the light exit surface of the third negative lens (3).

5. The plane wave based lighting system according to claim 3, characterized in that: The distance D between the first negative lens (1) and the second negative lens (2) is 12 and a distance D between the second negative lens (2) and the third negative lens (3) 23 Satisfaction: D 12 <D 23 .

6. The plane wave based lighting system according to claim 3, characterized in that: The effective focal length of the first lens group is f1 ′ satisfy: 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); The combined focal length F1 of the first negative lens (1) and the second negative lens (2) is ′ 2 Satisfaction: 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).

7. The plane wave based lighting system according to claim 6, characterized in that: 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: 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).

8. The plane wave based lighting system according to claim 1, characterized in that: The second lens group comprises a first meniscus lens (4), a second meniscus lens (5) and a first positive lens (6) which are arranged in sequence along the optical axis direction; The light-incoming surface and the light-outgoing surface of the first meniscus lens (4) both have a negative radius of curvature, and the first meniscus lens (4) is used to perform a first collimation on the laser light incident through the first lens group; The light-incoming surface and the light-outgoing surface of the second meniscus lens (5) both have a negative radius of curvature, 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 entrance surface and the light exit surface of the first positive lens (6) both have a negative radius of curvature, and the first positive lens (6) is used to perform a third collimation on the laser light incident through the second meniscus lens (5).

9. The plane wave based lighting system according to claim 8, characterized in that: 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|; Among them, r41 and r42 are respectively 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 respectively the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the second meniscus lens (5), and r61 and r62 are respectively the curvature radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens (6).

10. The plane wave based lighting system according to claim 9, characterized in that: The distance D between the first meniscus lens (4) and the second meniscus lens (5) is 45 Satisfy: 15mm<D 45 <16mm; The distance D between the second meniscus lens (5) and the first positive lens (6) is 56 Satisfy: 15mm<D 56 <16mm.

11. The plane wave based lighting system according to claim 8, characterized in that: The effective focal length f2 of the second lens group satisfies: 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); The combined focal length F4 of the first meniscus lens (4) and the second meniscus lens (5) is ′ 5 Satisfaction: 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).

12. The plane wave based lighting system according to claim 11, characterized in that: The effective focal length f2 of the first meniscus lens (4) ′ 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: Among them, r41 and r42 are respectively the curvature radius of the light incident surface and the curvature radius 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 radius of the light incident surface and the curvature radius 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 radius of the light incident surface and the curvature radius of the light emitting surface of the first positive lens (6), and d23 is the thickness of the first positive lens (6).

13. The plane wave based lighting system according to claim 3, characterized in that: The lighting system further comprises 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, and the moving range Δl of the third negative lens (3) satisfies the following condition with reference to the starting position of the third negative lens (3): -1.0mm≤Δl≤+1.0mm.

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

15. An exposure device, used in chip preparation process, characterized in that: Comprising a plane wave based illumination system as claimed in any one of claims 1 to 14.

Images