Mask

Abstract

This application relates to a photomask, including a transparent photomask substrate, a first functional layer and a second functional layer disposed on both sides of the transparent photomask substrate, and at least two probe holes. The probe holes longitudinally penetrate the transparent photomask substrate, the first functional layer, and the second functional layer, through which a probe of a device for acquiring position data passes. The first functional layer includes a first light-shielding layer and a first photoresist layer, or a pattern layer; the second functional layer includes a second light-shielding layer and a second photoresist layer, or a marking layer, the marking layer including at least two alignment marks. The probe can move to the marking layer to acquire the position data of the alignment marks, and the probe can move through the probe holes to the wafer to accurately acquire the position data of the reference marks located on the wafer. This facilitates nanoscale positioning and alignment of the wafer and the photomask during photolithography, improves the alignment accuracy during photolithography overlay, and prepares nanoscale aligned and overlaid images.

Description

Technical Field

[0001] This invention relates to a photomask and belongs to the field of semiconductor technology. Background Technology

[0002] As the integration of semiconductor chips continues to increase, the feature size of semiconductor chips is also shrinking with the development of Moore's Law. The continuous shrinking of feature size also increases the requirements for the overlay accuracy and feature size uniformity of photolithography processes.

[0003] Photolithography is a process that transfers a pattern from a photomask to a photoresist coated on a wafer surface through exposure. The pattern is then transferred to the wafer through processes such as development and etching. Photolithography directly determines the feature size and integration density of large-scale integrated circuits (LSI) and is a key process in LSI manufacturing. Common photolithography techniques include contact lithography, proximity lithography, projection lithography, direct-write lithography, and nanoimprint lithography. Contact lithography is the most traditional optical lithography method. Although it offers high resolution, its biggest drawback is the direct contact between the wafer and the photomask, which can easily damage and contaminate the photomask, reducing its lifespan. Proximity lithography solves the problems of photomask damage and contamination, but it struggles to meet the requirements of further reducing resolution, making it unsuitable for fabricating ultra-fine structures. Nanoimprint lithography mainly includes thermal embossing (HEL), extreme ultraviolet embossing (UV-NIL), and microcontact printing. Nanoimprint lithography is a low-cost and fast method for obtaining replica structures at the nanoscale. It can repeatedly prepare nanopatterned structures on large areas in large batches, and the high-resolution patterns produced have excellent uniformity and repeatability.

[0004] Semiconductor device manufacturing typically involves dozens of photolithography processes. To ensure the correspondence between each layer, alignment accuracy, i.e., overlay accuracy, must be matched with one-third of the photolithographic feature size. This is to achieve high-precision alignment between the current layer's photolithographic pattern and the pattern already formed in the previous layer, thereby improving the performance of semiconductor chips and the manufacturing yield.

[0005] Photolithography alignment refers to the process of aligning or centering the pattern on the photomask with the existing pattern on the wafer. This directly affects the control of critical dimensions and the accuracy of overlay. The alignment system of a photolithography machine can be divided into precise alignment between the photomask and the photomask stage, between the wafer and the wafer stage, between the photomask stage and the wafer stage, and between the photomask and the wafer. Photolithography alignment is mainly achieved through alignment marks on the photomask and the wafer, which determine the position and orientation. Currently, there are three methods for achieving alignment or measuring alignment accuracy: optical imaging, optical scattering, and scanning electron microscopy (SEM). Optical imaging is highly efficient, but its accuracy is limited by optical diffraction (optical wavelength); optical scattering is highly accurate and efficient, but requires setting up a test alignment pattern within a typical 10μm × 10μm area; and SEM is highly accurate but inefficient.

[0006] Chinese Patent 200410011339.8, "Repositioning Method Based on Atomic Force Microscope", discloses a method for repositioning an atomic force microscope using an optical measurement system and a mechanical positioning system to achieve overlay alignment. Its drawback is that the alignment accuracy is low and it is not suitable for nanoscale semiconductor processing technology.

[0007] Existing positioning techniques based on atomic force microscopy, which rely on optical measurement systems and mechanical positioning systems for repositioning, have their own limitations. On the one hand, the diffraction limit of optics theoretically restricts the application of optical systems in the measurement of nanoscale patterned structures. On the other hand, high-precision optical measurement systems and mechanical positioning systems are complex in structure and incompatible with atomic force microscopy equipment.

[0008] Furthermore, existing photomasks form alignment marks in the pattern layer. The probes of devices that acquire position data, such as atomic force microscopes, cannot pass through the photomask substrate to move onto the pattern layer, nor can they pass through the photomask to move onto the wafer surface located below the photomask. This results in a difference in the accuracy of measuring the position of the alignment marks on the pattern layer and the position of the marks on the wafer, thus reducing the alignment accuracy during photolithography overlay and making it impossible to achieve high-precision alignment between the photomask and the wafer. Summary of the Invention

[0009] The purpose of this invention is to provide a photomask having a first functional layer and a second functional layer disposed opposite to each other on a transparent photomask substrate. The first functional layer is used to form a pattern layer, and the second functional layer is used to form a marker layer. This allows the probe of a device for acquiring position data to move to the marker layer without passing through the transparent photomask substrate, thereby acquiring the position data of alignment marks in the marker layer with high accuracy. Furthermore, the photomask also has at least two probe holes through which the probe of the device for acquiring position data can pass. The probe can move to the wafer through the probe holes to accurately acquire the position data of the reference marks located on the wafer. This facilitates nanoscale positioning and alignment of the wafer and the photomask during photolithography, improving the alignment accuracy during photolithography overlay.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a mask, comprising:

[0011] Transparent mask substrate;

[0012] The first functional layer is disposed on one side of the transparent mask substrate;

[0013] A second functional layer is disposed on the side of the transparent mask substrate away from the first functional layer; and

[0014] At least two probe holes are provided, which extend longitudinally through the transparent mask substrate, the first functional layer, and the second functional layer, so that the probe of the device for acquiring position data can pass through them;

[0015] Wherein, the first functional layer includes a first light-shielding layer and a first photoresist layer disposed sequentially away from the transparent mask substrate, or the first functional layer is a pattern layer;

[0016] The second functional layer may include a second light-shielding layer and a second photoresist layer disposed sequentially away from the transparent mask substrate, or the second functional layer may be a marking layer, wherein the marking layer includes at least two alignment marks.

[0017] Furthermore, the alignment mark and the probe hole have a one-to-one correspondence, and the alignment mark is positioned close to the probe hole corresponding to it.

[0018] Furthermore, the distance between the alignment mark and its corresponding probe hole ranges from 0.1 to 1 mm.

[0019] Furthermore, the alignment mark can be any one or a combination of a circle, a cross, a polygon, an L-shaped pattern, and a T-shape.

[0020] Furthermore, the cross-sectional shape of the detection hole is any one of square, rectangular, circular, or trapezoidal.

[0021] Furthermore, the device for acquiring location data is a near-field scanning optical microscope.

[0022] Furthermore, the transparent mask substrate comprises synthetic quartz glass.

[0023] Furthermore, the mask also includes a phase-shifting layer disposed between the transparent mask substrate and the first functional layer.

[0024] Furthermore, the mask also includes an anti-reflection layer, which is disposed opposite to the transparent mask substrate on both sides of the second functional layer, and the probe hole extends longitudinally through the anti-reflection layer.

[0025] The beneficial effects of the present invention are as follows: the mask has a first functional layer and a second functional layer disposed opposite to each other on both sides of the transparent mask substrate. The first functional layer is used to form a pattern layer, and the second functional layer is used to form a marking layer. The alignment marks of the marking layer are easier to detect and have higher detection accuracy. The probe of the device for acquiring position data does not need to pass through the transparent mask substrate and can move to the marking layer to acquire the position data of the alignment marks. The mask also has at least two probe holes through which the probe of the device for acquiring position data can pass. The probe can move to the wafer through the probe holes to accurately acquire the position data of the reference marks located on the wafer. It is easy to achieve nanoscale positioning and alignment of the wafer and the mask during photolithography, improve the alignment accuracy during photolithography overlay, and prepare nanoscale aligned and overlaid images.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the mask plate shown in this invention.

[0028] Figure 2 This is a cross-sectional view of a mask according to the present invention.

[0029] Figure 3 This is a cross-sectional view of another mask plate shown in the present invention.

[0030] Figure 4 This is a structural diagram of the mask plate shown in this invention.

[0031] Figure 5 for Figure 1 Another cross-sectional view of the mask shown.

[0032] Figure 6 for Figure 3 Another cross-sectional view of the mask shown. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] 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.

[0035] Please see Figure 1The mask plate 1 shown in one embodiment of the present invention includes a transparent mask substrate 11, a first functional layer 12 disposed on one side of the transparent mask substrate 11, and a second functional layer 13 disposed on the side of the transparent mask substrate 11 away from the first functional layer 12. That is, the first functional layer 12 and the second functional layer 13 are disposed opposite to each other on both sides of the transparent mask substrate 11.

[0036] The transparent mask substrate 11 comprises synthetic quartz glass. The transparent mask substrate 11 may also be made of other materials, such as transparent resin substrates and other transparent glass substrates, without specific limitation herein. Preferably, the light transmittance of the transparent mask substrate 11 is greater than 85%.

[0037] Please see Figure 2 and Figure 3 The first functional layer 12 may include a first light-shielding layer 12-2 and a first photoresist layer 12-1 disposed sequentially away from the transparent mask substrate 11, or the first functional layer 12 may be a pattern layer 12.

[0038] The second functional layer 13 may include a second light-shielding layer 13-2 and a second photoresist layer 13-1 disposed sequentially away from the transparent mask substrate 11, or the second functional layer may be a marking layer 13.

[0039] For details, please see Figure 2 When the first functional layer 12 comprises a first light-shielding layer 12-2 and a first photoresist layer 12-1 disposed sequentially away from the transparent mask substrate 11, and the second functional layer 13 comprises a second light-shielding layer 13-2 and a second photoresist layer 13-1 disposed sequentially away from the transparent mask substrate 11, the mask 1 is a blank mask. Subsequently, a pattern layer 12 can be fabricated on the first light-shielding layer 12-2 using the first photoresist layer 12-1, and a marking layer 13 can be fabricated on the second light-shielding layer 13-2 using the second photoresist layer 13-1, as needed. The first photoresist layer 12-1 and the second photoresist layer 13-1 can be formed by spin coating or capillary coating, which are existing technologies and will not be described in detail here.

[0040] The materials of the first light-shielding layer 12-2 and the second light-shielding layer 13-2 can be chromium, but are not limited to this. The materials of the first light-shielding layer 12-2 and the second light-shielding layer 13-2 can also be chromium carbonitride, or chromium carbonitride and chromium nitride, which will not be listed here.

[0041] The first light-shielding layer 12-2 and the second light-shielding layer 13-2 can be prepared by sputtering deposition process, which is existing technology and will not be described in detail here.

[0042] It should be noted that the transparent mask substrate 11, the first light-shielding layer 12-2 and the second light-shielding layer 13-2, the first photoresist layer 12-1 and the second photoresist layer 13-1 can all be made of conventional materials and specifications in the art, including composition and thickness.

[0043] Please see Figure 3 When the first functional layer 12 is a pattern layer 12 and the second functional layer 13 is a marker layer 13, the mask 1 can be used to prepare patterns on a wafer using photolithography.

[0044] For ease of fabrication, the marking layer 13 and the pattern layer 12 can be fabricated simultaneously. The pattern layer 12 can be fabricated on the first light-shielding layer 12-2 using the first photoresist layer 12-1, and the marking layer 13 can be fabricated on the second light-shielding layer 13-2 using the second photoresist layer 13-1. However, the pattern layer 12 and the marking layer 13 can also be fabricated separately; no specific restrictions are imposed here, but this only increases the fabrication time. The fabrication methods for the pattern layer 12 and the marking layer 13 are existing technologies and will not be elaborated upon here.

[0045] The pattern layer 12 includes a nanostructure pattern, which is the pattern to be photolithographically etched. This nanostructure pattern includes several light-transmitting areas, opaque areas, or partially light-transmitting areas, thereby forming a fine pattern. The nanostructure pattern can be one-dimensional or two-dimensional.

[0046] The marking layer 13 includes at least two alignment marks. In this embodiment, the alignment marks are disposed on the side of the transparent mask substrate 11 away from the pattern layer 12. When the mask 1 needs to be scanned using a device for acquiring position data, the position data of the alignment marks can be acquired with high precision. Compared to forming the alignment marks in the pattern layer 12, the alignment marks of the mask 1 obtained in this embodiment are easier to detect and have higher detection accuracy. The probe can scan the alignment marks at close range without having to pass through the transparent mask substrate to scan the alignment marks located in the pattern layer 12, thus improving the accuracy of the position data.

[0047] Alignment marks can be any or a combination of circles, crosses, polygons, L-shaped patterns, and T-shapes, but are not limited to these; other shapes are also allowed, which are not listed here. At least two alignment marks can have the same or different shapes. The number of alignment marks can be two, three, four, or even more.

[0048] Preferably, the alignment marks are positioned close to the edge of the transparent mask substrate 11 to minimize obscuring the pattern structure of the pattern layer 12. The alignment marks can be located at the top corner or side of the transparent mask substrate 11.

[0049] Please see Figure 3The mask 1 also includes an anti-reflection layer 14, which is disposed opposite to the transparent mask substrate 11 on both sides of the second functional layer 13.

[0050] When the incident light beam shines on the mask 1, the antireflection layer 14 reduces light reflection and increases transmission, thereby improving light utilization efficiency. The antireflection layer 14 is a chromium-based compound. Optionally, the antireflection layer 14 is a metallic chromium-based compound containing oxygen and nitrogen. Preferably, the components of the antireflection layer 14 are one or more of chromium oxide, chromium oxynitride, and chromium carbonitride.

[0051] Clearly, the antireflective layer 14 is made of a transparent material, so that when the antireflective layer 14 is placed on the second functional layer 13, it does not obscure the second functional layer 13, thus ensuring the accuracy of the probe in acquiring the position data of the alignment mark.

[0052] In another embodiment, the mask 1 further includes a phase-shifting layer 15 disposed between the transparent mask substrate 11 and the first functional layer 12. The phase-shifting layer 15 can be made of molybdenum silicide, with a transmittance between 0-50% and a phase-shifting angle of 175 degrees to 185 degrees. The phase-shifting layer 15 can also be made of other materials; no specific limitations are imposed here, and it can be configured according to actual needs.

[0053] The phase-shifting layer 15 can be prepared by sputtering deposition, which is existing technology and will not be described in detail here. The phase-shifting layer 15 can use conventional materials and specifications in the art, including composition and thickness, and there is no limitation on simply adding other auxiliary layers between the corresponding layers of the mask 1.

[0054] When using mask 1 to photolithographically form a structure on a wafer, it is necessary to align the nanostructure pattern on mask 1 with the corresponding area of ​​the wafer. Furthermore, in order to form the desired structure on the wafer, overlay is generally required. To improve the alignment accuracy of the overlay, it is also necessary to align the nanostructure pattern on mask 1 with the corresponding area of ​​the wafer containing the structure.

[0055] Please see Figures 4 to 6 Mask 1 has a pattern to be lithographically patterned to form a pattern on the wafer. When mask 1 moves onto the wafer, it covers the reference marks located on the wafer, making them unscannable subsequently.

[0056] Therefore, the mask 1 also includes at least two probe holes 16, which extend longitudinally through the transparent mask substrate 11, the first functional layer 12 and the second functional layer 13, so that the probe of the device for acquiring position data can pass through to scan the reference mark located on the wafer.

[0057] Specifically, when the mask 1 also includes a first antireflection layer or an antireflection layer 14, the probe hole 16 extends longitudinally through the first antireflection layer or the antireflection layer 14. That is, the probe hole 16 extends longitudinally through the entire mask 1.

[0058] When the mask 1 moves onto the wafer, the probe hole 16 exposes the reference mark located on the wafer, and the probe passes through the probe hole 16 to reach the surface of the wafer. This enables the high-precision acquisition of the reference mark's position data.

[0059] The cross-sectional shape of the probe hole 16 can be any one of square, rectangular, circular, or trapezoidal, but is not limited to any of them; other shapes are also possible, which will not be listed here. At least two probe holes 16 can have the same or different shapes, which can be set according to actual needs, and no specific limitation is made here.

[0060] The cross-sectional dimensions of the probe aperture 16 are not specifically limited here, as long as they are large enough for the probe to pass through. They can be set based on the specific dimensions of the probe in an actual near-field scanning optical microscope. In a preferred embodiment, the cross-sectional dimensions of the probe aperture 16 can be less than 3mm*3mm, for example, 1mm*1mm.

[0061] Clearly, in order to expose the reference mark on the wafer, the cross-sectional size of the probe hole 16 is larger than the size of the reference mark.

[0062] The probe hole 16 is a through hole located near the edge of the transparent mask substrate 11, meaning it is located inside the surface of the transparent mask substrate 11. This arrangement minimizes the risk of disrupting the integrity of the pattern layer 12. Alternatively, the probe hole 16 can be a recess with an opening facing the side of the transparent mask substrate 11. The location of the probe hole 16 can be configured as needed.

[0063] The alignment marks and reference marks on the wafer described above can be selected from existing technologies in terms of shape, size, and position. It should be noted that, in order to facilitate identification by near-field scanning optical microscopes, the alignment marks and reference marks can be set to different structures to further improve measurement efficiency and improve the alignment accuracy between the mask 1 and the wafer.

[0064] Alignment marks and probe holes 16 have a one-to-one correspondence, with each alignment mark positioned close to its corresponding probe hole 16. That is, the number of alignment marks and probe holes 16 is the same. For each alignment mark, there is a reference mark located on the same side. Compared to the distance between this alignment mark and other reference marks, the distance between the reference mark on the same side and the alignment mark is the smallest. Based on a comparison between this minimum distance and a preset distance range, if the minimum distance falls within the preset distance range, the mask 1 and the wafer can be considered aligned.

[0065] The distance between the alignment mark and its corresponding probe hole 16 ranges from 0.1 to 1 mm.

[0066] Near-field scanning optical microscopy (NSOM) can be simply described as placing a subwavelength light source, such as a nanopore light source, in the near-field region of the sample (at a distance much smaller than the wavelength). The illuminated area of ​​the sample is determined only by the size of the light source or the aperture, and is independent of the wavelength of the light source. By scanning the light source and the sample against each other and detecting the light intensity signal, an optical image of the sample can be obtained. The resolution of this image is determined only by the size of the aperture, thus overcoming the diffraction limitation of traditional optical imaging caused by the wavelength of the light source.

[0067] Therefore, preferably, the device for acquiring position data is a near-field scanning optical microscope. When this mask 1 is used in semiconductor technology, the near-field scanning optical microscope overcomes the diffraction limitations of traditional optical microscopes, enabling imaging at the nanoscale and obtaining nanoscale coordinate data for reference and alignment marks. This allows for convenient and rapid, precise nanoscale alignment, thereby improving the quality of semiconductor chips.

[0068] In summary: The photomask has a first functional layer and a second functional layer disposed opposite to each other on the transparent photomask substrate. The first functional layer is used to form a pattern layer, and the second functional layer is used to form a marking layer. The alignment marks on the marking layer are easier to detect and have higher detection accuracy. The probe of the device for acquiring position data does not need to pass through the transparent photomask substrate and can move to the marking layer to acquire the position data of the alignment marks. The photomask also has at least two probe holes through which the probe of the device for acquiring position data can pass. The probe can move to the wafer through the probe holes to accurately acquire the position data of the reference marks located on the wafer. It is easy to achieve nanoscale positioning and alignment of the wafer and the photomask during photolithography, improve the alignment accuracy during photolithography overlay, and prepare nanoscale aligned and overlaid images.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A photomask, characterized in that, include: Transparent mask substrate; The first functional layer is disposed on one side of the transparent mask substrate; The second functional layer is disposed on the side of the transparent mask substrate away from the first functional layer; and At least two probe holes are provided, which extend longitudinally through the transparent mask substrate, the first functional layer, and the second functional layer, so that the probe of the device for acquiring position data can pass through them; Wherein, the first functional layer includes a first light-shielding layer and a first photoresist layer disposed sequentially away from the transparent mask substrate, or the first functional layer is a pattern layer; The second functional layer is a marking layer, which includes at least two alignment marks for photolithographic overlay alignment; The alignment mark and the probe hole have a one-to-one correspondence, and the alignment mark is positioned close to the probe hole corresponding to it. The distance between the alignment mark and its corresponding probe hole ranges from 0.1 to 1 mm.

2. The mask as described in claim 1, characterized in that, The alignment mark is any one or a combination of a circle, a cross, a polygon, an L-shaped pattern, and a T-shape.

3. The mask as described in claim 1, characterized in that, The cross-sectional shape of the detection hole can be any one of square, rectangular, circular, or trapezoidal.

4. The mask as described in claim 1, characterized in that, The device for acquiring location data is a near-field scanning optical microscope.

5. The photomask according to claim 1, characterized in that, The transparent mask substrate comprises synthetic quartz glass.

6. The photomask according to claim 1, characterized in that, The mask also includes a phase-shifting layer disposed between the transparent mask substrate and the first functional layer.

7. The mask as described in claim 1, characterized in that, The mask also includes an anti-reflection layer, which is disposed opposite to the transparent mask substrate on both sides of the second functional layer, and the probe hole extends longitudinally through the anti-reflection layer.

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