Lens array for wafer detection and wafer detection equipment

Abstract

The utility model provides a lens array for wafer detection and wafer detection equipment, belonging to the field of semiconductor detection, the lens array comprises a plurality of lenses with coplanar optical axes, the lenses are used for realizing an equivalent large numerical aperture, and each lens adopts spatially independent coherent / incoherent light illumination; an illumination light spot corresponding to each lens is independently modulated so as to realize the same illumination condition or different illumination conditions; the lens array provides multiple illumination modes at the same time through different illumination settings of each lens. The objective lens array and the illumination array are sequentially arranged along the scanning direction, a large effective numerical aperture which cannot be realized by a single objective lens can be realized, a large objective lens working distance is ensured, different numbers of lenses can be arranged along the scanning direction, and the working efficiency is improved. Meanwhile, the wafer defect detection system with multiple functions of multiple wavelengths, bright and dark field modes, different illumination modes and the like is realized, and the application range is widened.

Description

Technical Field

[0001] The utility model relates to the field of semiconductor detection, in particular to a lens array and wafer detection equipment for wafer detection. Background Art

[0002] In the field of optical inspection of wafer defects, high inspection accuracy and high inspection throughput require both a large numerical aperture and a large field of view of the objective lens in the optical system, and bright field and dark field microscopic imaging modes to detect defects of different scales and types in different nodes and processes. For inspection systems for wafer pattern processing defects ranging from tens of nanometers to a few nanometers, the working wavelength of its optical inspection is mainly limited to the ultraviolet to deep ultraviolet spectrum. Ultraviolet or deep ultraviolet objectives with large numerical aperture and large field of view have difficulties such as high difficulty in optical and optomechanical design, extremely high requirements for assembly and adjustment accuracy, high sensitivity to environmental factors, and short working distances that lead to harsh restrictions on machine system design. Utility Model Content

[0003] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a lens array and a wafer inspection device for wafer inspection, which can solve the above-mentioned problems.

[0004] A lens array for wafer inspection includes a plurality of lenses with coplanar optical axes, each lens adopts independent coherent / incoherent light illumination, and is used to achieve an equivalent large numerical aperture NA (Numerical Aperture, NA).

[0005] Furthermore, each lens of the lens array is adjustable, so that the illumination spot corresponding to each lens is modulated independently to achieve the same illumination condition or different illumination conditions.

[0006] Furthermore, the multiple lenses of the lens array are divided into multiple groups, and each group of lenses corresponds to a different working wavelength.

[0007] Furthermore, the lens array provides multiple lighting modes simultaneously by different lighting settings of each lens.

[0008] Furthermore, the multiple lenses of the objective lens array are arranged sequentially along the scanning direction of detection.

[0009] The utility model also provides a wafer inspection device, the objective lens of the inspection device adopts the aforementioned lens array, one lens in the lens array and the semi-transparent and semi-reflective mirror, the incident tube lens group corresponding to the bright field illumination incident light path, the magnification lens group and the imaging unit constitute a bright field inspection light path, the other lenses in the lens array respectively constitute a dark field inspection light path with the upstream corresponding aperture filter modulation unit, the magnification lens group and the imaging unit, and the multiple imaging units are connected to the image processor, and the received bright and dark field images are coupled through the image processor to perform defect screening and positioning.

[0010] Compared with the prior art, the beneficial effect of the utility model is that the present application adopts an objective lens array and an illumination array arranged in sequence along the scanning direction, which can achieve a large effective numerical aperture that cannot be achieved by a single objective lens, while ensuring a larger objective lens working distance. Each objective lens in the lens array collects wafer defect scattered light signals within different scattering angle ranges, and the scattering angle distribution of scattered light of different types of defects is different, so that the classification of wafer defects can be achieved based on the output image of each lens. This solution can arrange different numbers of lenses along the scanning direction, and at the same time realize a multifunctional wafer defect detection system including multi-wavelength, bright and dark field mode, different illumination modes, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of an example of a lens array of the present invention;

[0012] Figure 2 for Figure 1 Schematic diagram of equivalent numerical aperture distribution of examples;

[0013] Figure 3 for Figure 1 Schematic diagram of the illumination spot of the example;

[0014] Figure 4 Schematic diagram of different illumination modes of the lens array;

[0015] Figure 5 A schematic diagram of a lens array using two groups;

[0016] Figure 6 Schematic diagram of wafer inspection equipment.

[0017] In the figure, 1. semi-transparent and semi-reflective mirror; 2. incident tube lens group; 3. zoom lens group; 4. imaging unit; 5. aperture filter modulation unit; 6. image processor; 7. wafer stage. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] First embodiment

[0020] A lens array for wafer inspection, see Figure 1-Figure 4The lens array includes a plurality of lenses whose optical axes are coplanar, and each lens is illuminated by independent coherent / incoherent light to achieve an equivalent large numerical aperture NA.

[0021] See also Figure 1 In the example of , the lens array includes three lenses in the XZ plane: objective lens 1, objective lens 2 and objective lens 3. The multiple lenses of the objective lens array are arranged in sequence along the scanning direction of the detection, see Figure 1 The three lenses are arranged in sequence along the scanning direction (X direction in the figure) of the stage (also known as the electronically controlled scanning stage). The wafer sample passes through the field of view of each lens in turn to complete the optical image collection.

[0022] Through this lens array, a large effective numerical aperture that cannot be achieved with a single objective lens can be achieved, while ensuring a larger objective lens working distance and relaxing the mechanical design restrictions of the machine system.

[0023] The optical axis directions of the three lenses have a certain angle. In this example, the middle objective lens 2 is perpendicular to the electric-controlled scanning stage, that is, the stage setting of the wafer to be inspected, and the objective lenses 1 and 3 on both sides are symmetrically tilted relative to the objective lens 2, that is, the optical axis 1 of the objective lens 1 and the optical axis 3 of the objective lens 3 are symmetrically arranged relative to the optical axis 2 of the objective lens 2.

[0024] The illumination spot in the field of view of each lens is separated in the X direction and modulated independently to achieve the same or different illumination conditions. Different illumination conditions include incident angle, wavelength, and spot shape.

[0025] The center distance of wafer illumination from objective lens 1 to objective lens 2 is d1, and the center distance of wafer illumination from objective lens 3 to objective lens 2 is d2. d1 and d2 may be equal or unequal. The example shown in the figure is d1=d2.

[0026] The collection angle 1 of objective lens 1 and the collection angle 3 of objective lens 3 can be the same or different. The illustrated example shows a setting of collection angle 1 = collection angle 3.

[0027] The design of the lens array can achieve an equivalent large numerical aperture NA. The equivalent numerical aperture distribution is as follows: Figure 2 As shown in the figure, the NA value along the stage scanning direction can reach 0.99NA (collection half angle is about 82 degrees), and the NA value in the vertical scanning direction corresponds to the NA value of a single objective lens. At the same time, in the coherent laser illumination mode, the solution of achieving a large numerical aperture through a lens array can suppress the speckle effect in optical imaging and improve the signal-to-noise ratio of the detection results.

[0028] Through the lens array, each objective lens collects the scattered light signals of wafer defects within different scattering angle ranges. The scattering angle distribution of scattered light of different types of defects is different. Therefore, the wafer defects can be classified according to the output image of each lens. Therefore, it can be widely used in wafer inspection.

[0029] Among them, see Figure 3 of Figure 3 a and Figure 3 b. Each lens has its own independent illumination spot in its field of view, and each lens of the lens array is adjustable, so that the illumination spot corresponding to each lens can be modulated independently to achieve the same illumination conditions or different illumination conditions.

[0030] In this scheme, the defect structure in the wafer pattern passes through each lens in turn along the scanning direction. Under the same lighting conditions, the light field scattering angle distribution direction of different types of defect structures is different. Different lenses collect the defect scattered light with different scattering angle distribution and output images. Based on the image analysis taken by each lens, the classification of different types of defect structures can be realized to guide the wafer yield control scheme. In actual wafer inspection, the scattering signal of a certain type of defect structure under certain specific lighting conditions is very weak in the lens collection space, resulting in detection failure. In this case, different lens arrays can use different lighting conditions to reduce the probability of defect detection failure.

[0031] The lens array provides multiple lighting modes simultaneously through different lighting settings of each lens. Figure 4 , various lighting modes including but not limited to line spot lighting ( Figure 4 a) Spot scanning lighting ( Figure 4 b) etc.

[0032] See also Figure 5 , the multiple lenses of the lens array are divided into multiple groups, and each group of lenses corresponds to a different working wavelength. The lens array includes two groups, the first group includes objective lens 1, objective lens 2 and objective lens 3, and the second group includes objective lens 4, objective lens 5 and objective lens 6. The optical axis angle, collection angle size and center distance of wafer illumination of the two groups can be set to be the same. In this case, objective lens 2 of the first group and objective lens 5 of the second group can realize bright field and dark field imaging modes at the same time by introducing a coaxial illumination optical path.

[0033] Furthermore, the first group of objective lenses 1, 2 and 3 are based on working wavelength 1, and the second group of objective lenses 4, 5 and 6 are based on working wavelength 2, wherein working wavelengths 1 and 2 can select single wavelengths or wide spectrum wavelengths, thereby realizing multi-wavelength, wide and narrow spectrum wafer defect detection.

[0034] In summary, this solution can arrange different numbers of lenses along the scanning direction, and simultaneously realize a multifunctional wafer defect detection system including multi-wavelength, bright and dark field modes, and different illumination modes.

[0035] Second embodiment

[0036] A wafer inspection device, see Figure 6The objective lens of the detection equipment adopts the aforementioned lens array, one lens in the lens array and the semi-transparent and semi-reflective mirror 1, the incident tube lens group 2 corresponding to the bright field illumination incident light path, the zoom lens group 3 and the imaging unit 4 constitute a bright field detection light path, and the other lenses in the lens array respectively constitute a dark field detection light path with the upstream corresponding aperture filter modulation unit 5, the zoom lens group 3 and the imaging unit 4, and the multiple imaging units 4 are connected to the image processor 6, and the received bright and dark field images are coupled through the image processor 6 to perform defect screening and positioning.

[0037] The incident light path of bright field illumination includes a bright field illumination system and an autofocus system, which is irradiated onto the upper surface of the wafer on the wafer stage 7 through the incident tube lens group 2, the semi-transparent and semi-reflective mirror 1, and the objective lens.

[0038] The imaging unit 4 uses an image acquisition device such as a TDI sensor or a line scan camera.

[0039] The aperture filter modulation unit 5 includes an aperture component and a filter component, which are used to adjust and ensure the imaging quality of the dark field.

[0040] In the example shown, the lens array uses a group of 3 lenses, which can of course be expanded to Figure 5 Two or even three groups.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A lens array for wafer inspection, characterized in that: The lens array includes a plurality of lenses whose optical axes are coplanar; each lens of the lens array is adjustable, so that the illumination spot corresponding to each lens is independently modulated to achieve the same illumination condition or different illumination conditions; each lens adopts an independent coherent / incoherent light illumination to achieve an equivalent large numerical aperture NA.

2. The lens array according to claim 1, characterized in that: The multiple lenses of the lens array are divided into multiple groups, and each group of lenses corresponds to a different working wavelength.

3. The lens array according to claim 1, characterized in that: The lens array provides multiple lighting modes simultaneously through different lighting settings for each lens.

4. The lens array according to claim 1, characterized in that: The multiple lenses of the objective lens array are arranged in sequence along the scanning direction of detection.

5. A wafer inspection device, characterized in that: The objective lens of the detection device adopts the lens array described in any one of claims 1 to 4, one lens in the lens array and a semi-transparent and semi-reflective mirror (1), an incident tube lens group (2) corresponding to the bright field illumination incident light path, a zoom lens group (3) and an imaging unit (4) form a bright field detection light path, and other lenses in the lens array respectively form a dark field detection light path with an upstream corresponding aperture filter modulation unit (5), a zoom lens group (3) and an imaging unit (4), and a plurality of imaging units (4) are connected to an image processor (6), and the received bright and dark field images are coupled through the image processor to perform defect screening and positioning.

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