Photomask for defocusing amount detection of photoetching equipment, preparation method of photomask and detection equipment

Abstract

The invention provides a photomask for defocusing amount detection of photoetching equipment, a preparation method of the photomask and detection equipment, the photomask comprises a substrate layer and a light refraction body, the substrate layer comprises an upper surface and a lower surface which are oppositely arranged, and the concave wedge-shaped light refraction body is arranged on the upper surface and embedded in the substrate layer. According to the invention, the concave wedge-shaped light refraction body is arranged in the photomask, so that the height limitation of the light refraction body is reduced, and the risk that the focus measurement mask is broken by the library wall of the photomask where the mask is placed due to a convex wedge angle is avoided; meanwhile, the wedge angle of the concave wedge-shaped light refraction body can be randomly adjusted within the range of 0-90 degrees by utilizing the concave wedge-shaped light refraction body, so that the measurement sensitivity of the defocusing amount is improved; in addition, the preparation efficiency is improved in a mode of obtaining the photomask through the preparation mold, and the system error of defocusing amount measurement is reduced; and finally, the concave wedge-shaped light refraction body with symmetrical side walls is arranged, so that the accuracy of a measurement result is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit manufacturing, and in particular relates to a photomask used for detecting the defocus amount of a photolithography device, a preparation method thereof, and a detection device. Background Art

[0002] At present, in semiconductor process technology, photolithography technology is becoming more and more important with the improvement of key dimension technology. The stability of the exposure machine is affected by many factors, such as the offset of the wafer platform or lens on the exposure machine, the flatness of the wafer surface, the change of laser wavelength and the influence of the environment, which will cause the focal plane (focal length) of the exposure machine to change, that is, the actual focal length value of the exposure machine is different from the initial setting value, which will make the size and profile of the exposed wafer different from the preset value. In order to correct the change of the focal plane of the exposure machine in time, it is necessary to monitor the change of the focal plane of the exposure machine.

[0003] Leveling verification test (LVT) is a focus monitoring method for lithography equipment. In this method, convex wedge-shaped areas (as optical elements for diffracting light) are set on the upper surface / lower surface of certain areas of the mask, while no convex wedge-shaped areas are set in other areas. The wafer is exposed, and the light passing through the convex wedge-shaped areas is refracted and then diffracted by the mask, so that the light no longer propagates along the principal optical axis of the lens, and the imaging produces a horizontal offset; two images with image displacement (generated by the wedge-shaped area and the wedge-free area, respectively) are projected onto a wafer with photoresist, and the imaging offsets between the two projected images and the principal optical axis are measured by the OVL (Overlayer) tool to obtain the OVL value. The OVL value defines the correlation with different focus sets in the lithography equipment, so that the defocus amount of the lithography equipment can be quantified.

[0004] However, in the above method, the convex wedge-shaped area will make the height of the entire mask higher than that of a normal mask, thereby increasing the problem of collision between the mask and the wall of the mask library, resulting in mask breakage and contamination; at the same time, since the height of the convex wedge limits the wedge angle that can be adjusted in the wedge-shaped area, the defocus measurement sensitivity of the mask with the convex wedge is limited. Every 1 nanometer OVL change can only produce 5 nanometers of defocus, which cannot meet the requirements of advanced dry lithography equipment (such as ArF dry lithography equipment) for defocus measurement accuracy and sensitivity.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology part of the present application. Summary of the invention

[0006] In view of the above shortcomings of the prior art, an object of the present invention is to provide a mask for detecting the defocus amount of a lithography device, a preparation method thereof, and a detection device, so as to solve the problem that the LVT mask for measuring the defocus amount of the lithography device in the prior art has low sensitivity and is easy to break.

[0007] To achieve the above objectives, the present invention provides a mask for detecting the defocus amount of a lithography device, the mask comprising a substrate layer and a light refractor, the substrate layer comprising two oppositely disposed upper and lower surfaces, the upper surface being provided with a concave wedge-shaped light refractor embedded in the substrate layer.

[0008] Optionally, the light refraction body includes two side walls, the two side walls intersect at a bottom edge, one of the side walls is perpendicular to the substrate layer, and the angle between the other side wall and the substrate layer is an acute angle.

[0009] Optionally, the light refraction body includes two side walls, the two side walls intersect at a bottom edge, a surface passing through the bottom edge and perpendicular to the substrate layer is a first plane, the two side walls are symmetrical about the first plane, and the angles between the two side walls and the first plane are equal and acute angles.

[0010] Optionally, the upper end surface of the light refractor is not higher than the upper surface of the substrate layer, and the lower end surface of the light refractor is not lower than the lower surface of the substrate layer.

[0011] The present invention also provides a defocus detection device for a lithography device, the defocus detection device for a lithography device comprises any one of the above-mentioned masks for detecting the defocus of a lithography device, and also comprises: a light source, a lens group, a wafer and an imaging detection module, the light source is located above the mask, the lens group is arranged below the mask, and the wafer is arranged below the lens group; the light emitted by the light source is incident on a first position of the mask where the light refractor is arranged and a second position where the light refractor is not arranged, the light passes through the light refractor and the first position of the mask to form a first image on the wafer, and the light passes through the second position of the mask to form a second image on the wafer; the imaging detection module measures and calculates an imaging offset between the first image and the second image and compares the imaging offset with a defocus-imaging offset correspondence library of the lithography device to obtain the defocus of the lithography device.

[0012] The present invention further provides a method for preparing a photomask, the method for preparing the photomask used for any one of the above-mentioned photomasks for detecting defocus of a lithography device, the method comprising:

[0013] Providing a substrate layer, the substrate layer comprising an upper surface and a lower surface disposed opposite to each other;

[0014] Disposing a first photoresist convexly wedge-shaped on the upper surface of the substrate layer;

[0015] Using the first photoresist as a mask, etching the upper surface of the substrate layer to obtain the substrate layer including a convex wedge shape, and removing the first photoresist;

[0016] Exposing and developing the upper surface of the etched substrate layer to form a patterned second photoresist, wherein the second photoresist reveals a convex wedge shape of the substrate layer;

[0017] The convex wedge of the substrate layer is etched using the second photoresist as a mask to obtain the substrate layer including a concave wedge-shaped light refractor, and the second photoresist is removed to obtain a photomask.

[0018] The present invention further provides a method for preparing a photomask, the method for preparing the photomask used for any one of the above-mentioned photomasks for detecting defocus of a lithography device, the method comprising:

[0019] providing a mold substrate having a convex wedge shape;

[0020] Immersing the mold substrate including the convex wedge into a viscous quartz fluid at a preset temperature to perform imprint molding;

[0021] The quartz fluid enveloping the mold substrate is cooled to obtain a substrate layer including a concave wedge-shaped light refractor, and the mold substrate is removed to obtain a photomask.

[0022] Optionally, the method for preparing the mold substrate having a convex wedge shape is:

[0023] Providing a mold substrate, the mold substrate comprising an upper surface and a lower surface disposed opposite to each other;

[0024] Disposing a first photoresist convexly wedge-shaped on the upper surface of the mold substrate;

[0025] The upper surface of the mold substrate is etched using the first photoresist as a mask to obtain the mold substrate including a convex wedge shape, and the first photoresist is removed to obtain a mold substrate having a convex wedge shape.

[0026] Optionally, the method for setting the first photoresist convexly wedge-shaped is: obtaining the first photoresist in a stepped shape by n contact exposures, where n is greater than or equal to 2; and hot-melting the first photoresist in a stepped shape to obtain the first photoresist including the convexly wedge-shaped shape.

[0027] Optionally, the material of the mold substrate is silicon nitride, and the surface roughness of the mold substrate is 1-10 nanometers.

[0028] As described above, the mask for detecting the defocus amount of a lithography device and the preparation method and detection device thereof of the present invention have the following beneficial effects:

[0029] The present invention sets a concave wedge-shaped light refractor in the photomask as a photomask for detecting the defocus amount of the lithography equipment, thereby greatly reducing the height influence of the light refractor on the photomask, avoiding the risk of the convex wedge-shaped light refractor causing the focus measurement mask to collide with the wall of the photomask library where the mask is placed, and improving the compatibility of the photomask in the mask library of the mainstream lithography equipment;

[0030] The present invention utilizes a concave wedge-shaped light refractor so that the wedge angle of the light refractor can be arbitrarily adjusted within the range of 0°-90°, thereby improving the measurement sensitivity and accuracy of the imaging offset, thereby improving the measurement accuracy of the defocus amount, achieving a smaller defocus amount per unit OVL change, and greatly improving the sensitivity and accuracy of detecting the defocus amount;

[0031] The present invention can rapidly prepare photomasks in large quantities by using mold substrates, thus saving costs. At the same time, the specification parameters such as the shape and surface roughness of the photomasks can be unified, thereby reducing the systematic error of the photomask quality introduced by different photolithography-hot melt-etching processes, thereby reducing the systematic error of the focal length measurement result of the photolithography equipment stage.

[0032] The present invention provides a concave wedge-shaped light refractor with symmetrical side walls, and can form two OVL marks with opposite vector directions through one light refractor. By measuring the two OVL marks at the same position and taking the average of the absolute values, a more accurate OVL value can be obtained, thereby obtaining a more accurate correspondence to the defocus amount, and improving the accuracy of the measurement result.

[0033] The present invention prepares a light mask including a concave wedge-shaped light refractor, so that the method of preparing the light refractor changes from adding extra materials when setting a convex wedge in the traditional technology to reducing materials, thereby reducing the cost of the extra materials and lowering the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of a concave wedge-shaped light refractor in the first embodiment of the present invention.

[0035] Figure 2 It is a schematic diagram of a convex wedge-shaped light refractor in the prior art.

[0036] Figure 3 The figure shows a schematic diagram of a mask imaging process of a convex wedge-shaped light refractor in the prior art.

[0037] Figure 4 A schematic diagram of an OVL of a reticle imaging convex to a wedge-shaped light refractor in the prior art is shown.

[0038] Figure 5 A schematic diagram of a light mask showing a plurality of convex wedge-shaped light refractor arrays in the prior art is shown.

[0039] Figure 6 Shown is a schematic diagram of the mask imaging process in the first embodiment of the present invention.

[0040] Figure 7 It is a schematic diagram of the OVL-defocus relationship curve of the mask in the first embodiment of the present invention and the mask in the prior art.

[0041] Figure 8 Shown is a schematic diagram of a photomask in an optional example of an embodiment of the present invention.

[0042] Fig. 9 It is a schematic flow chart of the steps of the method for preparing a photomask in the third embodiment of the present invention.

[0043] Fig.10 The schematic diagram shows the structure of providing a substrate layer in step 1 of the method for preparing a photomask according to the third embodiment of the present invention.

[0044] Fig.11 Shown is a schematic structural diagram of forming a stepped first photoresist in an optional example of step 2 in the method for preparing a photomask in embodiment 3 of the present invention.

[0045] Fig.12 Shown is a schematic structural diagram of forming a first photoresist in a convex wedge shape in an optional example of step 2 in the method for preparing a photomask in embodiment 3 of the present invention.

[0046] Fig.13 It is a schematic structural diagram of forming a convex wedge-shaped substrate layer in step 3 of the method for preparing a photomask according to the third embodiment of the present invention.

[0047] Fig.14 Shown is a structural schematic diagram of etching the substrate layer in an optional example of step 3 in the method for preparing a mask in embodiment 3 of the present invention.

[0048] Fig.15 It is a schematic structural diagram of forming a second photoresist in step 4 of the method for preparing a photomask according to the third embodiment of the present invention.

[0049] Fig.16 It is a schematic structural diagram of forming a concave wedge-shaped substrate layer in step 5 of the method for preparing a photomask according to the third embodiment of the present invention.

[0050] Fig.17 It is a schematic flow chart of the steps of the method for preparing a photomask in the third embodiment of the present invention.

[0051] Fig.18 Shown is a schematic structural diagram of a mold substrate provided in an optional example of step 1 in the method for preparing a photomask in embodiment 4 of the present invention.

[0052] Fig.19 Shown is a schematic structural diagram of forming a stepped first photoresist in an optional example of step 1 in the method for preparing a photomask in embodiment 4 of the present invention.

[0053] Fig. 20 Shown is a schematic structural diagram of forming a first photoresist in a convex wedge shape in an optional example of step 1 in the method for preparing a photomask in embodiment 4 of the present invention.

[0054] Fig.21 Shown is a schematic structural diagram of a mold substrate having a convex wedge shape in an optional example of step 1 in the method for preparing a photomask in embodiment 4 of the present invention.

[0055] Fig. 22 It is a schematic structural diagram showing the step 2 of the method for preparing a photomask according to the fourth embodiment of the present invention, in which the mold substrate is immersed in a quartz fluid.

[0056] Fig.23 It is a schematic structural diagram of forming a concave wedge-shaped substrate layer in step 3 of the method for preparing a photomask according to the fourth embodiment of the present invention.

[0057] Description of Reference Numerals

[0058] 10. Photomask; 11. Substrate layer; 12. Convex wedge shape; 13. Concave wedge shape;

[0059] 21. Lens group; 22. Wafer; 23. Light; 24. Imaging offset; 25. Focus depth; 26. OVL mark;

[0060] 31. first photoresist; 32. second photoresist; 33. mold substrate; 34. quartz fluid;

[0061] M, shielding part; N, photolithography part; G, convex wedge-shaped light refractor; H, substrate; C, existing photomask. DETAILED DESCRIPTION

[0062] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0063] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the schematic diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0064] For convenience of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0065] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0066] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0067] Embodiment 1:

[0068] like Figure 1 As shown, the present invention provides a mask 10 for detecting the defocus amount of a lithography device, wherein the mask 10 includes a substrate layer 11 and a light refractor, wherein the substrate layer 11 includes two upper and lower surfaces that are relatively arranged, and the upper surface is provided with a concave wedge-shaped light refractor 13 embedded in the substrate layer 11.

[0069] Specifically, Figure 1 As shown, a light refractor having a concave wedge shape 13 is embedded in the substrate layer 11 .

[0070] In one embodiment, the substrate layer 11 is pure silica glass.

[0071] In the prior art, such as Figure 2 As shown, a convex wedge-shaped light refractor G is embedded on a substrate H to form an existing mask C. The existing mask C is used as a focus measurement mask for measuring focal length. It is placed in a mask library, and the wall of the mask library surrounds the existing mask C. Figure 3 As shown, light passes through the convex wedge-shaped light refractor G and is refracted in region ②, then diffracted by the substrate H, and finally light interference occurs at point A or B, forming an image within the range of the focus depth 25, and generating a lateral offset; while light passes through the wedge-free region ① and is finally projected at the intersection between the Z axis and the wafer 22 plane, forming an image within the range of the focus depth 25, and generating no lateral offset; the image obtained by measuring the imaging of the wedge-shaped region ② including the convex wedge-shaped light refractor G and the wedge-free region ① is as shown in FIG. Figure 4The difference between the OVL mark 26 shown in FIG. 1 and FIG. 2 is used to obtain the imaging offset 24 generated by the wedge-shaped area. The imaging offset 24 corresponds to a specific defocus amount of the lithography device. The imaging offset 24 is matched with the pre-obtained imaging offset 24-defocus amount correspondence library to determine the defocus amount at this time, such as Figure 5 The figure shows a mask composed of an array of multiple convex wedge-shaped light refractors G. However, the convex wedge-shaped light refractors G greatly increase the height of the existing mask C, which is easy to collide with the wall of the mask library to break the mask or pollute the mask library, and the wedge angle that can be achieved with the convex wedge-shaped light refractors G with limited height is also limited, and the maximum can only reach 8°, thereby reducing the imaging offset that can be generated by a unit defocus amount by 24, and the 1 nanometer OVL (overlay alignment) change can only reflect a 5 nanometer defocus amount, and the sensitivity of detecting the defocus amount is low.

[0072] The present invention provides a light refractor with a concave wedge shape 13 in the mask 10 as the mask 10 for detecting the defocus amount of the lithography equipment, thereby greatly reducing the height influence of the light refractor on the mask 10, avoiding the risk of collision between the light refractor and the wall of the mask library, and improving the compatibility of the mask 10 in the mask library of the mainstream lithography equipment; in addition, the wedge angle of the light refractor with a concave wedge shape 13 can also be made larger, such as 15.8°, so that the OVL change of 1 nanometer can reflect the defocus amount of 2.5 nanometers, such as Figure 6 As shown, the sensitivity of detecting the defocus amount is greatly improved, which is conducive to meeting the accuracy requirements of the defocus amount detection of the 248 nm KrF lithography equipment, such as Figure 7 As shown, the change in OVL value E produced by unit defocus amount of the concave wedge 13 of the present invention is greater than the OVL value F produced by unit defocus amount of the convex wedge 12 in the prior art.

[0073] In one embodiment, the light refractor includes two side walls, the two side walls intersect at a bottom edge, one of the side walls is perpendicular to the substrate layer 11 , and the angle between the other side wall and the substrate layer 11 is an acute angle.

[0074] In one embodiment, Figure 8 As shown, the light refraction body includes two side walls, the two side walls intersect at a bottom edge, the surface passing through the bottom edge and perpendicular to the substrate layer 11 is a first plane, the two side walls are symmetrical about the first plane, and the angles between the two side walls and the first plane are equal and both are acute angles.

[0075] The present invention sets symmetrical side walls through a light refractor, and can form two OVL marks 26 with opposite vector directions through one light refractor. By measuring the average of the absolute values ​​of the two OVL marks 26 at the same position, a more accurate OVL value can be obtained, thereby obtaining a more accurate correspondence to the defocus amount.

[0076] In one embodiment, the upper end surface of the light refractor is not higher than the upper surface of the substrate layer 11 , and the lower end surface of the light refractor is not lower than the lower surface of the substrate layer 11 .

[0077] Embodiment 2:

[0078] like Figure 6 As shown, the present invention also provides a defocus detection device for a lithography device, the defocus detection device for the lithography device includes the mask 10 for defocus detection of the lithography device described in any one of the first embodiments, and also includes: a light source, a lens group 21, a wafer 22 and an imaging detection module, the light source is located above the mask 10, the lens group 21 is arranged below the mask 10, and the wafer 22 is arranged below the lens group 21; the light 23 emitted by the light source is incident on a first position of the mask 10 where the light refractor is arranged and a second position where the light refractor is not arranged, the light 23 passes through the light refractor and the first position of the mask 10 to form a first image on the wafer 22, and the light 23 passes through the second position of the mask 10 to form a second image on the wafer 22; the imaging detection module measures and calculates an imaging offset 24 between the first imaging and the second imaging and compares the imaging offset 24 with a corresponding relationship library of the defocus amount-imaging offset 24 of the lithography device to obtain the defocus amount of the lithography device.

[0079] The present invention uses the mask 10 including the concave wedge-shaped light refractor 13 for the defocus detection device of the lithography device, which can improve the measurement sensitivity and accuracy of the imaging offset 24, thereby improving the measurement accuracy of the defocus.

[0080] Embodiment three:

[0081] like Fig. 9 As shown, the present invention further provides a method for preparing a mask 10, the method for preparing the mask 10 for detecting the defocus amount of a lithography device as described in any one of the above-mentioned embodiments 1, the method comprising:

[0082] S1: providing a substrate layer 11, wherein the substrate layer 11 comprises an upper surface and a lower surface which are arranged opposite to each other;

[0083] S2: Disposing a first photoresist 31 convex toward the wedge shape 12 on the upper surface of the substrate layer 11;

[0084] S3: using the first photoresist 31 as a mask to etch the upper surface of the substrate layer 11 to obtain the substrate layer 11 including the convex wedge 12, and removing the first photoresist 31;

[0085] S4: exposing and developing the upper surface of the etched substrate layer 11 to form a patterned second photoresist 32, wherein the second photoresist 32 reveals the convex wedge shape 12 of the substrate layer 11;

[0086] S5: using the second photoresist 32 as a mask to etch the convex wedge 12 of the substrate layer 11 to obtain the substrate layer 11 including a light refraction body of the concave wedge 13, and removing the second photoresist 32 to obtain the photomask 10.

[0087] The method for preparing the photomask of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the above sequence does not strictly represent the sequence of the method for preparing the photomask protected by the present invention, and those skilled in the art may change it according to the actual preparation steps.

[0088] First, if Fig.10 As shown, step S1 is performed to provide a substrate layer 11, wherein the substrate layer 11 includes an upper surface and a lower surface that are oppositely disposed.

[0089] In one embodiment, the substrate layer 11 is made of silicon dioxide.

[0090] In one embodiment, the substrate layer 11 has a length of 7.2 mm, a width of 7.2 mm, and a height of 2.88 mm.

[0091] Then, step S2 is performed to form a first photoresist 31 protruding toward the wedge shape 12 on the upper surface of the substrate layer 11 .

[0092] In one embodiment, the method of setting the first photoresist 31 convex to the wedge shape 12 is as follows: Fig.11 As shown, the first photoresist 31 is obtained in a stepped manner by n times of contact exposure, where n is greater than or equal to 2; Fig.12 As shown, the first stepped photoresist 31 is thermally melted to obtain the first photoresist 31 including the convex wedge shape 12 .

[0093] Then, if Fig.13 As shown, step S3 is performed, wherein the upper surface of the substrate layer 11 is etched using the first photoresist 31 as a mask to obtain the substrate layer 11 including the convex wedge 12 , and the first photoresist 31 is removed.

[0094] In one embodiment, the upper surface of the substrate layer 11 is etched by dry etching, such as Fig.14 As shown, during the etching process, the first photoresist 31 blocks the blocked portion M below it and the bottom of the convex wedge 12 close to the upper surface of the substrate layer 11 and is not etched, and only the other photoresist portions N not blocked by the first photoresist 31 are etched, thereby obtaining the substrate layer 11 including the convex wedge 12.

[0095] Then, if Fig.15 As shown, S4 is performed to form a patterned second photoresist 32 after exposure and development on the upper surface of the etched substrate layer 11 , wherein the second photoresist 32 reveals the convex wedge shape 12 of the substrate layer 11 .

[0096] In one embodiment, the etched area of ​​the second photoresist 32 pattern is defined by non-contact exposure.

[0097] Finally, if Fig.16 As shown, S5 is performed, using the second photoresist 32 as a mask to etch the convex wedge 12 of the substrate layer 11 to obtain a light refraction body including a concave wedge 13 ; the second photoresist 32 is removed from the substrate layer 11 to obtain a photomask 10 .

[0098] The present invention prepares the light mask 10 including the light refractor of the concave wedge 13, so that the method of preparing the light refractor changes from adding extra materials when setting the convex wedge in the traditional technology to reducing materials, thereby reducing the cost of the extra materials and lowering the manufacturing cost.

[0099] Embodiment 4:

[0100] like Fig.17 As shown, the present invention further provides a method for preparing a mask 10, the method for preparing the mask 10 for detecting the defocus amount of a lithography device as described in any one of the above-mentioned embodiments 1, the method comprising:

[0101] Step 1: providing a mold substrate 33 having a convex wedge shape 12;

[0102] Step 2: immersing the mold substrate 33 including the convex wedge 12 into a viscous quartz fluid 34 at a preset temperature for embossing;

[0103] Step 3: Cool the quartz fluid 34 that wraps the mold substrate 33 to obtain a substrate layer 11 including a light refraction body with a concave wedge shape 13 , remove the mold substrate 33 , and obtain a photomask 10 .

[0104] The method for preparing the photomask of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the above sequence does not strictly represent the sequence of the method for preparing the photomask protected by the present invention, and those skilled in the art may change it according to the actual preparation steps.

[0105] First, step 1 is performed to provide a mold substrate 33 having a convex wedge shape 12 .

[0106] In one embodiment, the melting point of the material of the mold substrate 33 is much higher than the maximum viscous flow temperature of glass, and the viscous flow temperature of glass is 1713° C.-1723° C.

[0107] In one embodiment, the mold substrate 33 is made of silicon nitride.

[0108] In one embodiment, the surface roughness of the mold substrate 33 is 1-10 nanometers.

[0109] In one embodiment, a method of preparing a mold substrate 33 having a convex wedge shape 12 includes:

[0110] S1: Fig.18 As shown, a mold substrate 33 is provided, and the mold substrate 33 includes an upper surface and a lower surface that are oppositely arranged;

[0111] S2: Fig.19 As shown, the first photoresist 31 is obtained in a stepped manner by n times of contact exposure, where n is greater than or equal to 2; Fig. 20 As shown, the first step-shaped photoresist 31 is heat-melted to obtain a first photoresist 31 convex to a wedge shape;

[0112] S3: Fig.21 As shown, the upper surface of the mold substrate 33 is etched using the first photoresist 31 as a mask to obtain the mold substrate 33 including the convex wedge 12 , and the first photoresist 31 is removed to obtain the mold substrate 33 having the convex wedge 12 .

[0113] Specifically, S2 is a method for forming the first photoresist 31 convexly wedge-shaped, which can also be obtained by other feasible methods.

[0114] Then, if Fig. 22 As shown, step 2 is performed to immerse the mold substrate 33 including the convex wedge 12 into a viscous quartz fluid 34 at a preset temperature for imprint molding.

[0115] In one embodiment, the temperature for performing the imprint molding is 1713°C-1723°C.

[0116] Finally, if Fig.23 As shown, step 3 is performed to cool the quartz fluid 34 wrapping the mold substrate 33 to obtain a substrate layer 11 including a light refraction body of a concave wedge 13 , and the mold substrate 33 is removed to obtain a photomask 10 .

[0117] The present invention can rapidly prepare the photomask 10 in large quantities by using the mold substrate 33, thereby saving costs. At the same time, the shape, surface roughness and other specification parameters of the photomask 10 can be unified, thereby reducing the systematic error in the quality of the photomask 10 introduced by different photolithography-hot melt-etching processes, thereby reducing the systematic error in the focal length measurement result of the photolithography equipment stage. At the same time, by preparing the photomask 10 including the concave wedge-shaped light refractor 13, the method of preparing the light refractor is changed from adding additional materials when setting the convex wedge in the traditional technology to reducing materials, thereby reducing the cost of the additional materials required and reducing the manufacturing cost.

[0118] In summary, the photomask used for defocus detection of a lithography device of the present invention, its preparation method, and the detection device can reduce the height limit of the light refractor by setting a concave wedge-shaped light refractor in the photomask, thereby avoiding the risk of the focus measurement mask being smashed by the wall of the photomask library where the mask is placed due to the convex wedge angle; at the same time, the concave wedge-shaped light refractor is used to make the wedge angle of the light refractor arbitrarily adjustable in the range of 0°-90°, thereby improving the measurement sensitivity of the defocus amount; in addition, the preparation efficiency is improved by preparing a mold to obtain the photomask, thereby reducing the systematic error of the defocus measurement; finally, the accuracy of the measurement result is improved by setting a concave wedge-shaped light refractor with symmetrical side walls.

[0119] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0120] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A mask for detecting defocus of a lithography device, characterized in that: The light mask comprises a substrate layer and a light refractor. The substrate layer comprises an upper surface and a lower surface which are arranged opposite to each other. A concave wedge-shaped light refractor is arranged on the upper surface and embedded in the substrate layer.

2. The photomask for detecting defocus of a lithography device according to claim 1, characterized in that: The light refractor comprises two side walls, the two side walls intersect at a bottom edge, one of the side walls is perpendicular to the substrate layer, and the angle between the other side wall and the substrate layer is an acute angle.

3. The photomask for detecting defocus of a lithographic device according to claim 1, characterized in that: The light refractor includes two side walls, which intersect at a bottom edge. The surface passing through the bottom edge and perpendicular to the substrate layer is a first plane. The two side walls are symmetrical about the first plane, and the angles between the two side walls and the first plane are equal and acute.

4. The photomask for detecting defocus of a lithographic device according to claim 1, characterized in that: The upper end surface of the light refractor is not higher than the upper surface of the substrate layer, and the lower end surface of the light refractor is not lower than the lower surface of the substrate layer.

5. A defocus detection device for a lithography device, characterized in that: The defocus detection device of the lithography equipment includes the mask for defocus detection of the lithography equipment according to any one of claims 1 to 4, and also includes: a light source, a lens group and an imaging detection module, the light source is located above the mask, the lens group is arranged below the mask, and the wafer is arranged below the lens group; the light emitted by the light source is incident on a first position of the mask where the light refractor is arranged and a second position where the light refractor is not arranged, the light passes through the light refractor and the first position of the mask to form a first image on the wafer, and the light passes through the second position of the mask to form a second image on the wafer; the imaging detection module measures and calculates the imaging offset between the first image and the second image and compares the imaging offset with a defocus amount-imaging offset correspondence library of the lithography equipment to obtain the defocus amount of the lithography equipment.

6. A method for preparing a photomask, characterized in that: The preparation method is used to prepare the mask for defocus detection of a lithography device according to any one of claims 1 to 4, and the preparation method comprises: Providing a substrate layer, the substrate layer comprising an upper surface and a lower surface disposed opposite to each other; Disposing a first photoresist convexly wedge-shaped on the upper surface of the substrate layer; Using the first photoresist as a mask, etching the upper surface of the substrate layer to obtain the substrate layer including a convex wedge shape, and removing the first photoresist; Exposing and developing the upper surface of the etched substrate layer to form a patterned second photoresist, wherein the second photoresist reveals a convex wedge shape of the substrate layer; The convex wedge of the substrate layer is etched using the second photoresist as a mask to obtain the substrate layer including a concave wedge-shaped light refractor, and the second photoresist is removed to obtain a photomask.

7. A method for preparing a photomask, characterized in that: The preparation method is used to prepare the mask for defocus detection of a lithography device according to any one of claims 1 to 4, and the preparation method comprises: providing a mold substrate having a convex wedge shape; Immersing the mold substrate including the convex wedge into a viscous quartz fluid at a preset temperature to perform imprint molding; The quartz fluid enveloping the mold substrate is cooled to obtain a substrate layer including a concave wedge-shaped light refractor, and the mold substrate is removed to obtain a photomask.

8. The method for preparing a photomask according to claim 7, characterized in that: The method for preparing the mold substrate having a convex wedge shape is: Providing a mold substrate, the mold substrate comprising an upper surface and a lower surface disposed opposite to each other; Disposing a first photoresist convexly wedge-shaped on the upper surface of the mold substrate; The upper surface of the mold substrate is etched using the first photoresist as a mask to obtain the mold substrate including a convex wedge shape, and the first photoresist is removed to obtain a mold substrate having a convex wedge shape.

9. The method for preparing a photomask according to any one of claims 6 or 8, characterized in that: The method for setting the first photoresist in a convex wedge shape is: obtaining the first photoresist in a stepped shape by performing n times of contact exposure, where n is greater than or equal to 2; The first stepped photoresist is thermally melted to obtain a first photoresist having a convex wedge shape.

10. The method for preparing a photomask according to claim 7, characterized in that: The material of the mold substrate is silicon nitride, and the surface roughness of the mold substrate is 1-10 nanometers.

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