Wafer alignment system of photoetching machine

Abstract

The invention relates to the technical field of photoetching machines, in particular to a wafer alignment system of a photoetching machine. The wafer alignment system of the photoetching machine comprises a wide-angle lens used for imaging at least two alignment marks on a wafer; and the effective imaging unit is used for imaging effective imaging parts, corresponding to the at least two alignment marks, in an image imaged by the wide-angle lens onto a target surface of an imaging camera. Thus, through the combination of the wide-angle lens and the effective imaging unit, at least two alignment marks on the wafer are imaged at a time, so that the yield is improved by observing a larger range, and the utilization rate of the target surface of the imaging camera is increased.

Description

Technical Field

[0001] The present application relates to the technical field of photolithography machines, and more specifically, to a wafer alignment system for a photolithography machine. Background Art

[0002] The photolithography machine is an important equipment in the semiconductor manufacturing process. Its function is to accurately transfer the circuit pattern in the mask (also known as the photomask) to the wafer according to the predetermined size and position through the exposure process.

[0003] The wafer alignment system in a lithography machine is responsible for aligning the pattern on the mask with the existing pattern on the wafer to ensure accurate overlay between the patterns after exposure. This alignment step occurs before lithography, and the accuracy of this alignment directly affects overlay precision.

[0004] At present, image alignment is a commonly used method in the wafer alignment system of a lithography machine. This method generally uses an optical system, such as a microscope system, to magnify the alignment mark on the wafer, that is, the target, and image it onto an imaging camera, such as the target surface of a CCD.

[0005] However, this commonly used image alignment method can generally only detect one target on the wafer at a time, which reduces the efficiency of the entire system.

[0006] Therefore, it is desirable to provide an improved wafer alignment system for a photolithography machine. Summary of the Invention

[0007] An embodiment of the present application provides a lithography machine wafer alignment system, which images at least two alignment marks on a wafer at one time by using a combination of a wide-angle lens and an effective imaging unit, thereby improving productivity by observing a larger range and increasing the utilization rate of the target surface of the imaging camera.

[0008] According to one aspect of the present application, a photolithography machine wafer alignment system is provided, which includes: a wide-angle lens for imaging at least two alignment marks on a wafer; and an effective imaging unit for imaging the effective imaging portion corresponding to the at least two alignment marks in the image imaged by the wide-angle lens onto a target surface of an imaging camera.

[0009] In the above-mentioned lithography machine wafer alignment system, the effective imaging unit images the effective imaging portion corresponding to the at least two alignment marks onto the target surface of the imaging camera in a magnified imaging manner.

[0010] In the above-mentioned lithography machine wafer alignment system, the effective imaging unit includes: a folding mirror, used to reflect the imaging light corresponding to the at least two alignment marks in the image imaged by the wide-angle lens; and a fine-tuning mirror, used to receive the imaging light reflected by the folding mirror and adjust the position of the imaging light projected onto the target surface of the camera.

[0011] In the above-mentioned lithography machine wafer alignment system, the at least two alignment marks include a first alignment mark and a second alignment mark, and the folding mirror and the fine-tuning mirror include a first group of folding mirrors and fine-tuning mirrors arranged on the opposite side of the first alignment mark relative to the optical axis of the imaging camera, and a second group of folding mirrors and fine-tuning mirrors arranged on the opposite side of the second alignment mark relative to the optical axis of the imaging camera.

[0012] The above-mentioned lithography machine wafer alignment system further includes: a turning reflector, located between the wide-angle lens and the wafer, for projecting light from the wafer to the wide-angle lens through turning.

[0013] In the above-mentioned lithography machine wafer alignment system, the wide-angle lens includes the first lens group to the sixth lens group in sequence from the object plane to the image plane, and the wide-angle lens further includes an aperture located between the third lens group and the fourth lens group.

[0014] In the above-mentioned lithography machine wafer alignment system, the surface of the first mirror group facing the object plane is a spherical surface with a curvature radius of 54.4, a thickness of 7.6 mm, and a material refractive index of 1.83, and the surface facing the image plane is a spherical surface with a curvature radius of 195.2 and a thickness of 1.5 mm; the surface of the second mirror group facing the object plane is a spherical surface with a curvature radius of -216.1, a thickness of 3.0 mm, and a material refractive index of 1.73, and the surface facing the image plane is a spherical surface with a curvature radius of 55.4 and a thickness of 4.7 mm; the first surface of the third mirror group from the object plane to the image plane is a spherical surface with a curvature radius of 163.1, a thickness of 4.0 mm, and a material refractive index of 1.85, and the second surface is a spherical surface with a curvature radius of 5775.6, a thickness of 3.5 mm, a material refractive index of 1.83, and the surface facing the image plane is a spherical surface with a curvature radius of -99.6 and a thickness of 0.5 mm; the surface of the aperture is a spherical surface. , the radius of curvature is infinite, and the thickness is 14.2mm; the first surface of the fourth lens group from the object plane to the image plane is a spherical surface with a radius of curvature of -35.7, a thickness of 7.8mm, and a material refractive index of 1.73; the second surface is a spherical surface with a radius of curvature of -82.5, a thickness of 6.6mm, and a material refractive index of 1.83, and the surface facing the image plane is a spherical surface with a radius of curvature of -48.1 and a thickness of 0.5mm; the surface of the fifth lens group facing the object plane is a spherical surface with a radius of curvature of -221.5, a thickness of 4.5mm, and a material refractive index of 1.85, and the surface facing the image plane is a spherical surface with a radius of curvature of 447.5 and a thickness of 660mm; and the surface of the sixth lens group facing the object plane is a spherical surface with a radius of curvature of -412.5, a thickness of 8.8mm, and a material refractive index of 1.80, and the surface facing the image plane is a spherical surface with a radius of curvature of -69.4 and a thickness of 2.1mm.

[0015] The lithography machine wafer alignment system provided in the embodiment of the present application can image at least two alignment marks on the wafer at one time by using a combination of a wide-angle lens and an effective imaging unit, thereby improving productivity by observing a larger range and increasing the utilization rate of the target surface of the imaging camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Various other advantages and benefits of the present application will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The drawings in the specification are intended only to illustrate preferred embodiments and are not to be construed as limiting the present application. Obviously, the drawings described below are merely examples of the present application, and those skilled in the art can derive other drawings based on these drawings without inventive effort. Throughout the drawings, the same reference numerals denote the same components.

[0017] Figure 1A schematic diagram of a wafer alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0018] Figure 2 A schematic diagram of an application scenario of a wafer alignment system for a lithography machine according to an embodiment of the present application is illustrated.

[0019] Figure 3 The figure illustrates a functional schematic diagram of an effective imaging unit of a wafer alignment system of a lithography machine according to an embodiment of the present application.

[0020] Figure 4A and Figure 4B The figure illustrates a light path schematic diagram of a specific example of a lithography machine wafer alignment system according to an embodiment of the present application.

[0021] Figure 5 The figure shows a schematic diagram of the composition of a specific example of a wafer alignment system for a lithography machine according to an embodiment of the present application.

[0022] Figure 6 The figure shows a schematic diagram of the lens group composition of the wide-angle lens of the wafer alignment system of the lithography machine according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] Below, the exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the exemplary embodiments described herein.

[0024] Figure 1 FIG2 is a schematic diagram of a wafer alignment system for a lithography machine according to an embodiment of the present application. Figure 1 As shown, in a lithography machine wafer alignment system according to an embodiment of the present application, a wide-angle lens is used to image at least two alignment marks on a wafer. Furthermore, to address the issue of wide-angle lens imaging causing effective imaging portions to be difficult to be received by the lithography objective lens, the system further includes an effective imaging unit for imaging the effective imaging portions corresponding to the at least two alignment marks in the image captured by the wide-angle lens onto a target surface of an imaging camera.

[0025] Therefore, according to an embodiment of the present application, the lithography machine wafer alignment system includes: a wide-angle lens for imaging at least two alignment marks on the wafer; and an effective imaging unit for imaging the effective imaging part corresponding to the at least two alignment marks in the image imaged by the wide-angle lens onto the target surface of the imaging camera.

[0026] Figure 2 FIG2 is a schematic diagram showing an application scenario of a lithography machine wafer alignment system according to an embodiment of the present application. Figure 2 As shown in (a), when the photolithography objective lens is required to expose the wafer, as shown in Figure 2 As shown in (b), the wafer is first moved to a wide-angle wafer alignment system, and alignment is performed by imaging at least two alignment marks on the wafer. Specifically, Figure 2 (b) shows two alignment marks as an example.

[0027] In an embodiment of the present application, when the alignment mark on the wafer is imaged onto an imaging camera, such as a CCD, through a wide-angle lens, a certain magnification ratio will be formed. Since the imaging field of view of the wide-angle lens is large, it can cover a larger field of view range, generally exceeding tens of millimeters to hundreds of millimeters. Therefore, after magnification through the wide-angle lens, its imaging field of view will be larger, while the target surface of a general CCD is a few millimeters to tens of millimeters, and it is impossible to reach a target surface size of hundreds of millimeters. Moreover, in fact, the size of a single target on the wafer is relatively small, generally ranging from hundreds of microns to one millimeter. Therefore, the target distance generated by the two exposure fields is generally far, which is also related to the magnification of the main objective lens and the size of the mask. Generally, for the mainstream I-line lithography machines on the market, the wafer alignment target distance between the two exposure fields is about 33mm (specifically related to the mask mark design). After magnified imaging, the image field of view will be much larger than 33mm, making it impossible for a normal CCD to receive it. Figure 3 Therefore, in the lithography machine wafer alignment system according to the embodiment of the present application, the effective imaging unit images the effective imaging portion corresponding to the at least two alignment marks in the image imaged by the wide-angle lens onto the target surface of the imaging camera, and preferably, the effective imaging unit further images the effective imaging portion corresponding to the at least two alignment marks onto the target surface of the imaging camera in a magnified imaging manner, as shown in FIG. Figure 3 as shown in (b). Figure 3 The figure illustrates a functional schematic diagram of an effective imaging unit of a wafer alignment system of a lithography machine according to an embodiment of the present application.

[0028] In this way, the wafer alignment system of the lithography machine according to the embodiment of the present application combines a wide-angle lens with an effective imaging unit to project useful images onto the target surface of the imaging camera and eliminate useless areas, thereby achieving the purpose of observing multiple targets at a time and realizing the purpose of magnified imaging.

[0029] That is, in the wafer alignment system of the lithography machine according to the embodiment of the present application, the effective imaging unit images the effective imaging portion corresponding to the at least two alignment marks onto the target surface of the imaging camera in an enlarged imaging manner.

[0030] Furthermore, in the lithography machine wafer alignment system according to the embodiment of the present application, at least two alignment marks are imaged using a wide-angle lens, and the effective imaging unit images the effective imaging portions corresponding to the at least two alignment marks onto the same target surface of the lithography objective lens, which can reduce systematic errors. In other words, if multiple small-field-of-view imaging systems are used to image and align the at least two alignment marks separately, there will be large systematic errors between the systems, and extremely high requirements for installation precision will be imposed. Moreover, the stability will be lower than that of the single imaging system according to the embodiment of the present application.

[0031] Below, an implementation example of an effective imaging unit in a wafer alignment system of a lithography machine according to an embodiment of the present application will be described in detail.

[0032] Figure 4A and Figure 4B The figure shows a light path diagram of a specific example of a lithography machine wafer alignment system according to an embodiment of the present application. Figure 4A The figure shows a schematic plan view of the optical path of a specific example of the lithography machine wafer alignment system, and Figure 4B The figure shows a schematic three-dimensional diagram of the optical path of a specific example of the lithography machine wafer alignment system. Figure 4A and Figure 4B As shown, the wafer alignment system for a lithography machine according to an embodiment of the present application includes a wide-angle lens, a folding mirror, and a fine-tuning mirror. Specifically, the folding mirror and the fine-tuning mirror constitute an effective imaging unit for magnifying the effective imaging portion of the image formed by the wide-angle lens corresponding to the at least two alignment marks and imaging it onto the target surface of the imaging camera.

[0033] Therefore, in the lithography machine wafer alignment system according to an embodiment of the present application, the effective imaging unit includes: a folding mirror for reflecting the imaging light corresponding to the at least two alignment marks in the image imaged by the wide-angle lens; and a fine-tuning mirror for receiving the imaging light reflected by the folding mirror and adjusting the position of the imaging light projected onto the target surface of the camera.

[0034] Furthermore, as shown in FIG4 , when imaging two alignment marks, based on the optical path characteristics of light divergence from wide-angle lens imaging, each set of folding mirrors and fine-tuning mirrors is respectively disposed on opposite sides of the alignment marks relative to the optical axis of the imaging camera. That is, in the wafer alignment system for a lithography machine according to an embodiment of the present application, the at least two alignment marks include a first alignment mark and a second alignment mark, and the folding mirrors and fine-tuning mirrors include a first set of folding mirrors and fine-tuning mirrors disposed on opposite sides of the first alignment mark relative to the optical axis of the imaging camera, and a second set of folding mirrors and fine-tuning mirrors disposed on opposite sides of the second alignment mark relative to the optical axis of the imaging camera.

[0035] Figure 5 FIG2 is a schematic diagram showing a composition of a specific example of a wafer alignment system for a lithography machine according to an embodiment of the present application. Figure 5 As shown, the wide-angle lens, folding mirror, and fine-tuning mirror in the wafer alignment system of a lithography machine according to an embodiment of the present application are respectively implemented as predetermined lenses on the imaging light path. A specific example of the wide-angle lens is as follows, where the lens parameters are in the order from right to left (the right side is near the wafer surface):

[0036]

[0037] The first to sixth lens groups are all wide-angle lens groups, and the folding mirror and fine-tuning mirror are plane mirrors and are placed between the sixth lens and the image plane. Figure 6 shown. Figure 6 The figure shows a schematic diagram of the lens group composition of the wide-angle lens of the wafer alignment system of the lithography machine according to an embodiment of the present application.

[0038] Therefore, in the wafer alignment system of the lithography machine according to the embodiment of the present application, the wide-angle lens includes the first lens group to the sixth lens group in sequence from the object plane to the image plane, and the wide-angle lens further includes an aperture located between the third lens group and the fourth lens group.

[0039] Moreover, in the above-mentioned lithography machine wafer alignment system, the surface of the first mirror group facing the object plane is a spherical surface with a curvature radius of 54.4 and a thickness of 7.6 mm, and the material refractive index is 1.83, and the surface facing the image plane is a spherical surface with a curvature radius of 195.2 and a thickness of 1.5 mm.

[0040] Moreover, in the above-mentioned lithography machine wafer alignment system, the surface of the second mirror group facing the object plane is a spherical surface with a curvature radius of -216.1, a thickness of 3.0 mm, and a material refractive index of 1.73, and the surface facing the image plane is a spherical surface with a curvature radius of 55.4 and a thickness of 4.7 mm.

[0041] Moreover, in the above-mentioned lithography machine wafer alignment system, the first surface of the third mirror group from the object plane to the image plane is a spherical surface with a curvature radius of 163.1, a thickness of 4.0 mm, and a material refractive index of 1.85; the second surface is a spherical surface with a curvature radius of 5775.6, a thickness of 3.5 mm, and a material refractive index of 1.83; and the surface facing the image plane is a spherical surface with a curvature radius of -99.6 and a thickness of 0.5 mm.

[0042] Furthermore, in the above-mentioned lithography machine wafer alignment system, the surface of the aperture is a spherical surface with an infinite radius of curvature and a thickness of 14.2 mm.

[0043] Moreover, in the above-mentioned lithography machine wafer alignment system, the first surface of the fourth mirror group from the object plane to the image plane is a spherical surface with a curvature radius of -35.7, a thickness of 7.8 mm, and a material refractive index of 1.73; the second surface is a spherical surface with a curvature radius of -82.5, a thickness of 6.6 mm, and a material refractive index of 1.83; and the surface facing the image plane is a spherical surface with a curvature radius of -48.1 and a thickness of 0.5 mm.

[0044] Moreover, in the above-mentioned lithography machine wafer alignment system, the surface of the fifth mirror group facing the object plane is a spherical surface with a curvature radius of -221.5, a thickness of 4.5 mm, and a material refractive index of 1.85, and the surface facing the image plane is a spherical surface with a curvature radius of 447.5 and a thickness of 660 mm.

[0045] Moreover, in the above-mentioned lithography machine wafer alignment system, the surface of the sixth mirror group facing the object plane is a spherical surface with a curvature radius of -412.5 and a thickness of 8.8 mm, and the material refractive index is 1.80, and the surface facing the image plane is a spherical surface with a curvature radius of -69.4 and a thickness of 2.1 mm.

[0046] Furthermore, in the lithography machine wafer alignment system according to an embodiment of the present application, a deflecting mirror is preferably included between the wide-angle lens and the wafer, the deflecting mirror being used to deflect light from the wafer and project it onto the wide-angle lens. The deflecting mirror is used because the space below the lithography objective is generally very limited, and thus, the deflecting mirror can avoid structural interference with the objective system.

[0047] That is, in the lithography machine wafer alignment system according to the embodiment of the present application, it further includes: a turning reflector, located between the wide-angle lens and the wafer, for projecting the light from the wafer to the wide-angle lens through turning.

[0048] To sum up, according to the embodiment of the present application, the lithography machine wafer alignment system uses a wide-angle lens to align the target on the wafer, which can observe a larger range at a time, thereby improving the yield; on the other hand, it eliminates the invalid imaging part and images the effective imaging part onto the target surface, effectively increasing the utilization rate of the target surface of the imaging camera.

[0049] The basic principles of this application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to being implemented using the above specific details.

[0050] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0051] It should also be noted that in the apparatus, device, and method of the present application, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0052] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0053] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A wafer alignment system for a photolithography machine, wherein: include: a wide-angle lens for imaging at least two alignment marks on the wafer; as well as, The effective imaging unit is used to image the effective imaging portion corresponding to the at least two alignment marks in the image formed by the wide-angle lens onto the target surface of the imaging camera.

2. The wafer alignment system for a lithography machine according to claim 1, wherein: The effective imaging unit images the effective imaging portion corresponding to the at least two alignment marks onto the target surface of the imaging camera in a magnified imaging manner.

3. The wafer alignment system for a lithography machine according to claim 2, wherein: The effective imaging unit includes: a folding reflector, configured to reflect imaging light corresponding to the at least two alignment marks in an image formed by the wide-angle lens; and The fine-tuning reflector is used to receive the imaging light reflected by the folding reflector and adjust the position of the imaging light projected onto the target surface of the camera.

4. The wafer alignment system for a lithography machine according to claim 3, wherein: The at least two alignment marks include a first alignment mark and a second alignment mark, and the folding mirror and the fine-tuning mirror include a first group of folding mirrors and a fine-tuning mirror arranged on the opposite side of the first alignment mark relative to the optical axis of the imaging camera, and a second group of folding mirrors and a fine-tuning mirror arranged on the opposite side of the second alignment mark relative to the optical axis of the imaging camera.

5. The wafer alignment system for a lithography machine according to claim 3, wherein: Further including: The deflection reflector is located between the wide-angle lens and the wafer, and is used to deflect the light from the wafer and project it onto the wide-angle lens.

6. The wafer alignment system for a lithography machine according to claim 1, wherein: The wide-angle lens comprises, from the object plane to the image plane, a first lens group to a sixth lens group, and a stop located between the third lens group and the fourth lens group.

7. The wafer alignment system for a lithography machine as claimed in claim 6, wherein The surface of the first lens group facing the object plane is a spherical surface with a curvature radius of 54.4, a thickness of 7.6 mm, and a material refractive index of 1.83, and the surface facing the image plane is a spherical surface with a curvature radius of 195.2 and a thickness of 1.5 mm; The surface of the second lens group facing the object plane is a spherical surface with a curvature radius of -216.1 and a thickness of 3.0mm. The refractive index of the material is 1.

73. The surface facing the image plane is also a spherical surface with a curvature radius of 55.4 and a thickness of 4.7mm. The first surface of the third lens group from the object plane to the image plane is a spherical surface with a curvature radius of 163.1, a thickness of 4.0 mm, and a material refractive index of 1.85; the second surface is a spherical surface with a curvature radius of 5775.6, a thickness of 3.5 mm, and a material refractive index of 1.83; and the surface facing the image plane is a spherical surface with a curvature radius of -99.6 and a thickness of 0.5 mm; The surface of the aperture is a spherical surface with an infinite radius of curvature and a thickness of 14.2 mm; The first surface of the fourth lens group from the object plane to the image plane is a spherical surface with a curvature radius of -35.7, a thickness of 7.8 mm, and a material refractive index of 1.73; the second surface is a spherical surface with a curvature radius of -82.5, a thickness of 6.6 mm, and a material refractive index of 1.83; and the surface facing the image plane is a spherical surface with a curvature radius of -48.1 and a thickness of 0.5 mm; The surface of the fifth lens group facing the object plane is a spherical surface with a curvature radius of -221.5 and a thickness of 4.5 mm, and the refractive index of the material is 1.85, and the surface facing the image plane is a spherical surface with a curvature radius of 447.5 and a thickness of 660 mm; and The surface of the sixth lens group facing the object plane is a spherical surface with a curvature radius of -412.5, a thickness of 8.8 mm, and a material refractive index of 1.80, and the surface facing the image plane is a spherical surface with a curvature radius of -69.4 and a thickness of 2.1 mm.

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