Mask plate absorption layer preparation method, mask plate and preparation method thereof

Abstract

The disclosure provides a mask plate absorption layer preparation method, a mask plate and a preparation method thereof, and relates to the field of photolithography technology. The mask plate absorption layer preparation method comprises the following steps: obtaining a mask substrate; and preparing an actual absorption layer on the surface of the mask substrate by ion beam deposition, wherein the stress of the actual absorption layer is regulated by changing the relative angle between the mask substrate and a target material during ion beam deposition to adjust the inclination angle between the incident direction of target particles required for preparing the actual absorption layer and the direction perpendicular to the surface of the mask substrate, so as to control the deformation amount and / or surface figure PV of the surface of the mask substrate.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of photolithography, and in particular to a mask blank absorption layer preparation method, a mask blank and a preparation method thereof. BACKGROUND

[0002] In the manufacturing process of a micro-nano photolithography mask blank, the deposition of the absorption layer is a very important step and is also the basis for the pattern processing of the mask blank. As a common method for preparing the absorption layer, magnetron sputtering can obtain a relatively dense film layer. However, when the metal material is sputtered and deposited by a radio frequency power source, the power of the radio frequency power source cannot be too large, otherwise the voltage will be unstable and the glow will flicker. It is relatively difficult for the magnetron sputtering method to obtain a more dense film layer, and at this time, ion beam deposition (IBD) is needed to prepare the absorption layer.

[0003] When the metal absorption layer is prepared by ion beam deposition, due to the high energy of the deposited particles and the large surface migration ability, a high-density thin film close to a bulk material can be obtained, and the optical properties and mechanical properties of the prepared thin film are excellent. However, the prepared thin film also has an ultra-high bulk density, so that the film layer usually presents a high stress state, and as the thickness of the film layer increases, the accumulated stress in the film layer will cause serious surface shape distortion of the mask, introduce a large error, and affect the exposure uniformity and overlay accuracy. When the stress accumulates to a certain degree or reaches a certain threshold, the thin film may even warp, crack, and fall off, which greatly affects the subsequent processing and use as a mask absorption layer. SUMMARY

[0004] Therefore, the first aspect of the embodiments of the present disclosure provides a mask blank absorption layer preparation method, which comprises: obtaining a mask substrate; and preparing an actual absorption layer on the surface of the mask substrate by ion beam deposition, wherein the stress of the actual absorption layer is adjusted by changing the relative angle between the mask substrate and the target material during ion beam deposition to adjust the inclination angle between the incident direction of the target particles required for preparing the actual absorption layer and the direction perpendicular to the surface of the mask substrate, and the deformation amount and / or surface shape PV of the surface of the mask substrate are controlled.

[0005] According to an embodiment of the present disclosure, the method further comprises: obtaining a first surface profile of the mask substrate without the predetermined absorption layer formed on the surface; preparing the predetermined absorption layer with different predetermined deposition thicknesses on the mask substrate at a plurality of predetermined relative angles respectively, obtaining a second surface profile of the mask substrate with the predetermined absorption layer with each predetermined deposition thickness formed on the surface respectively; calculating a stress of the predetermined absorption layer with each predetermined deposition thickness on the surface of the mask substrate according to a profile curvature variation between the second surface profile and the first surface profile of the predetermined absorption layer with each predetermined deposition thickness respectively; fitting the stress of the predetermined absorption layer with each predetermined deposition thickness on the surface of the mask substrate at the plurality of predetermined relative angles to form a stress-tilt angle curve corresponding to the predetermined absorption layer with different deposition thicknesses; and repeating the above operations to obtain the stress-tilt angle curve of the predetermined absorption layer with different deposition thicknesses and different material types.

[0006] According to an embodiment of the present disclosure, the method further comprises: obtaining a first surface profile of the mask substrate without the predetermined absorption layer formed on the surface; preparing the predetermined absorption layer with different material types on the mask substrate at a plurality of predetermined relative angles respectively, obtaining a second surface profile of the mask substrate with the predetermined absorption layer with each material type formed on the surface respectively; calculating a stress of the predetermined absorption layer with each material type on the surface of the mask substrate according to a profile curvature variation between the second surface profile and the first surface profile of the predetermined absorption layer with each material type respectively; fitting the stress of the predetermined absorption layer with each material type on the surface of the mask substrate at the plurality of predetermined relative angles to form a stress-tilt angle curve corresponding to the predetermined absorption layer with different material types; and repeating the above operations to obtain the stress-tilt angle curve of the predetermined absorption layer with different deposition thicknesses and different material types.

[0007] According to an embodiment of the present disclosure, the method further comprises: obtaining a first surface profile of the mask substrate without the predetermined absorption layer formed on the surface; preparing the predetermined absorption layer with different material types on the mask substrate at a plurality of predetermined relative angles respectively, obtaining a second surface profile of the mask substrate with the predetermined absorption layer with each material type formed on the surface respectively; calculating a stress of the predetermined absorption layer with each material type on the surface of the mask substrate according to a profile curvature variation between the second surface profile and the first surface profile of the predetermined absorption layer with each material type respectively; fitting the stress of the predetermined absorption layer with each material type on the surface of the mask substrate at the plurality of predetermined relative angles to form a stress-tilt angle curve corresponding to the predetermined absorption layer with different material types; and repeating the above operations to obtain the stress-tilt angle curve of the predetermined absorption layer with different deposition thicknesses and different material types.

[0008] According to an embodiment of the present disclosure, the material of the actual absorption layer comprises one of Cr, Ta, Mo, MoSi and MoTa.

[0009] According to an embodiment of the present disclosure, the thickness of the actual absorption layer is 38 nm-42 nm.

[0010] According to an embodiment of the present disclosure, the predetermined tilt angle is 10°-60°.

[0011] According to an embodiment of the present disclosure, the material of the mask substrate comprises sapphire or fused quartz.

[0012] A second aspect of the embodiments of the present disclosure provides a preparation method of a mask blank, comprising: preparing an absorption layer of the mask blank by using the preparation method described above; and obtaining the mask blank when the deformation amount and / or the surface figure PV of the mask substrate surface meet the preset condition.

[0013] A third aspect of the embodiments of the present disclosure provides a mask blank, which is prepared by using the preparation method described above.

[0014] The mask blank absorption layer preparation method, the mask blank and the preparation method thereof provided by the embodiments of the present disclosure at least have the following technical effects:

[0015] In the process of preparing the absorption layer by using the ion beam deposition, the relative angle between the mask substrate and the target material during the ion beam deposition is changed to adjust the inclination angle between the incident direction of the target particles required for preparing the absorption layer and the surface of the mask substrate, so as to control the stress of the absorption layer, thereby offsetting the influence of the stress of the absorption layer on the surface figure of the mask blank, greatly reducing the change amount of the surface figure of the mask blank before and after the absorption layer is plated, and avoiding the influence of the deformation of the mask substrate on the pattern processing uniformity, the position error of the photomask and the subsequent pattern replication process.

[0016] The method has universality and is not limited to the control of the stress of the mask blank absorption layer and the control of the surface figure of the mask blank. For more extensive substrate deformation control requirements, the method can also be applied to control the surface figure. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure, taken in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A flow chart of the mask blank absorption layer preparation method according to an embodiment of the present disclosure is schematically shown.

[0019] Figure 2 A principle diagram of the mask blank absorption layer preparation method according to an embodiment of the present disclosure is schematically shown.

[0020] Figure 3 A stress-inclination angle curve diagram corresponding to the absorption layer formed by the same predetermined deposition thickness and different types of materials according to an embodiment of the present disclosure is schematically shown.

[0021] Figure 4A A stress diagram of a Cr film layer when the deposition inclination angle is 60° according to an embodiment of the present disclosure is schematically shown.

[0022] Figure 4BA stress diagram of a Cr film layer with a deposition angle of 48° is schematically shown according to an embodiment of the present disclosure.

[0023] Figure 4C A stress diagram of a Cr film layer with a deposition angle of 30° is schematically shown according to an embodiment of the present disclosure.

[0024] Figure 4D A stress diagram of a Cr film layer with a deposition angle of 20° is schematically shown according to an embodiment of the present disclosure.

[0025] Figure 4E A stress diagram of a Cr film layer with a deposition angle of 10° is schematically shown according to an embodiment of the present disclosure.

[0026] Figure 5 A result diagram of a Cr film layer stress regulation process repeatability verification is schematically shown according to an embodiment of the present disclosure.

[0027] Figure 6A A surface shape diagram of a mask substrate with a deposition angle of 60° is schematically shown according to an embodiment of the present disclosure.

[0028] Figure 6B A surface shape diagram of a mask substrate with a deposition angle of 48° is schematically shown according to an embodiment of the present disclosure.

[0029] Figure 6C A surface shape diagram of a mask substrate with a deposition angle of 30° is schematically shown according to an embodiment of the present disclosure.

[0030] Figure 6D A surface shape diagram of a mask substrate with a deposition angle of 20° is schematically shown according to an embodiment of the present disclosure.

[0031] Figure 6E A surface shape diagram of a mask substrate with a deposition angle of 10° is schematically shown according to an embodiment of the present disclosure.

[0032] Figure 7A A surface shape diagram of a 6-inch center thinning mask substrate before film plating is schematically shown according to an embodiment of the present disclosure.

[0033] Figure 7B A surface shape diagram of a 6-inch center thinning mask substrate after film plating is schematically shown according to an embodiment of the present disclosure.

[0034] Figure 8A A surface shape diagram of a 6-inch center thinning mask substrate 26x33mm standard field before film plating is schematically shown according to an embodiment of the present disclosure.

[0035] Figure 8BThe post-coating face shape of the 6-inch center thinning mask substrate 26x33mm standard field after coating is schematically shown. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to specific embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present disclosure.

[0037] The terms used herein are only used to describe specific embodiments, and are not intended to limit the present disclosure. The terms "include", "contain" and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0038] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure or description thereof. The description referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the description, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0039] In addition, the terms "first", "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features. In the description of the present disclosure, the meaning of "multiple" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0040] In the process of implementing the present disclosure, it is found that the Cr film layer has high absorption rate for light of a specific wavelength range and high adhesion on a transparent substrate, so it can be used as an absorption layer material for a photomask. When using ion beam sputtering to prepare the Cr film layer, sputtering deposition needs to be carried out at a high ion source voltage and a low cavity pressure. The Cr film layer prepared in this way has a large residual stress, which will cause the substrate to deform, causing adverse effects on the uniformity of pattern processing, position error and subsequent pattern replication process of the photomask.

[0041] Ion beam deposition can reduce the internal stress of the deposited Cr film layer by adjusting the sputtering chamber pressure and changing the process gas. However, there is a certain limit to adjusting the stress by this method, which cannot completely meet the shape requirements of the mask plate absorption layer. In addition, the absorption rate of the Cr film layer at a specific wavelength will also be reduced to a certain extent, affecting the subsequent processing technology of the mask plate. Other absorption layers also have similar problems.

[0042] Therefore, embodiments of the present disclosure aim to provide a mask plate absorption layer preparation method, a mask plate and a preparation method thereof, which can reduce the influence of absorption layer stress on the deformation of the substrate before and after film deposition under the premise of ensuring the absorption rate of the absorption layer, and provide a new technical route for effectively inhibiting the influence of absorption layer stress on the shape of the mask plate substrate. The following will be described in detail in combination with specific embodiments.

[0043] Figure 1 A flowchart of a mask plate absorption layer preparation method according to an embodiment of the present disclosure is schematically shown.

[0044] As shown in Figure 1 , the mask plate absorption layer preparation method of the present embodiment can include operation S110 to operation S140.

[0045] In operation S110, a mask substrate is obtained.

[0046] In operation S120, an actual absorption layer is prepared on the surface of the mask substrate by ion beam deposition, wherein the stress of the actual absorption layer is adjusted by changing the relative angle between the mask substrate and the target material during ion beam deposition to adjust the inclination angle between the incident direction of the target particles required for preparing the actual absorption layer and the direction perpendicular to the surface of the mask substrate, and the deformation amount and / or the PV of the surface shape of the mask substrate are controlled.

[0047] In some embodiments of the present disclosure, the mask substrate may, for example, include sapphire or fused quartz with any surface shape. The specific type of mask substrate can be selected according to actual application requirements, which is not limited in the present disclosure. The actual absorption layer can be understood as the absorption layer that needs to be prepared in the process of preparing the finished mask plate.

[0048] Figure 2 A schematic diagram of the principle of the mask plate absorption layer preparation method according to an embodiment of the present disclosure is shown.

[0049] As shown in Figure 2As shown, the tilted deposition (tilt angle a) employed by ion beam deposition results in anisotropic microstructure of the deposited film, which leads to anisotropic stress behavior of the film. Exemplarily, along the incident flux direction (e.g. y direction), the ballistic shadowing increases the column separation and allows the structure to relax. In contrast, there is no shadowing in the orthogonal direction to restrict growth. Therefore, the columns can fan out in the x direction and are more prone to chain together, thus reducing the stress level of the film. The tilted deposition increases the porosity of the film, decouples the columnar microstructure, and allows the structure to relax at short length scales. Therefore, the total film stress tends to decrease with increasing deposition angle.

[0050] According to embodiments of the present disclosure, the stress magnitude and type corresponding to different materials of the absorption layer and different thicknesses of the absorption layer can be different, and the corresponding tilt angle can also be different. In order to accurately select the tilt angle for different materials of the absorption layer and different thicknesses of the absorption layer in the process of preparing the absorption layer, preferably, the optimal tilt angle range corresponding to different materials of the absorption layer and different thicknesses of the absorption layer needs to be determined in advance.

[0051] Based on this, in some embodiments of the present disclosure, the preparation method can further include:

[0052] obtaining a first surface profile of a mask substrate whose surface is not formed with a predetermined absorption layer.

[0053] preparing a predetermined absorption layer with a plurality of predetermined deposition thicknesses on the mask substrate at a plurality of predetermined relative angles respectively, to obtain a second surface profile of the mask substrate whose surface is formed with the predetermined absorption layer with each predetermined deposition thickness.

[0054] calculating the stress magnitude of the predetermined absorption layer with each predetermined deposition thickness on the surface of the mask substrate according to the profile curvature variation between the second surface profile and the first surface profile corresponding to the predetermined absorption layer with each predetermined deposition thickness respectively.

[0055] fitting the stress magnitude of the predetermined absorption layer with each predetermined deposition thickness on the surface of the mask substrate at the plurality of predetermined relative angles to form a stress-tilt angle curve corresponding to the predetermined absorption layer with different deposition thicknesses.

[0056] repeating the above operation to obtain the stress-tilt angle curve of the predetermined absorption layer with different material types at different deposition thicknesses.

[0057] Similarly, in some other embodiments of the present disclosure, the preparation method can further include:

[0058] obtaining a first surface profile of a mask substrate whose surface is not formed with a predetermined absorption layer;

[0059] The predetermined absorption layers of different material types are prepared on the mask substrate at a plurality of predetermined relative angles respectively, to obtain a second surface profile of the mask substrate with the predetermined absorption layers of different material types respectively formed on the surface;

[0060] The stress of the predetermined absorption layer of each predetermined material type on the surface of the mask substrate is calculated according to the change in the surface profile curvature between the second surface profile corresponding to the predetermined absorption layer of each predetermined material type and the first surface profile;

[0061] The stress of the predetermined absorption layer of each predetermined material type on the surface of the mask substrate is fitted at a plurality of predetermined relative angles, to form a stress-tilt angle curve corresponding to the predetermined absorption layer of different material types;

[0062] The stress-tilt angle curve of the predetermined absorption layer of different deposition thicknesses under different material types is obtained by repeating the above operations.

[0063] For example, for the absorption layer of the same material, the predetermined absorption layer of different deposition thicknesses required can be plated on the mask substrate at a plurality of predetermined angles. The surface profile of the mask substrate is measured by the stress meter before and after the predetermined absorption layer is plated. The stress meter calculates the stress of the plated film layer on the substrate according to the change in the surface profile curvature of the mask substrate before and after the film is plated. Then, the stress-tilt angle curve is obtained by fitting the stress of the required absorption layer, and the corresponding stress control route is formulated: when the ion beam deposition sputtering is changed, the relative angle between the mask substrate and the target material is changed, so that the incident direction of the target particles presents a certain tilt angle with the mask substrate, so as to offset the influence of the absorption layer stress on the surface profile of the mask.

[0064] Based on the above operations, the stress-tilt angle curve of the predetermined absorption layer of different material types under different thicknesses can be obtained. Subsequently, based on the stress-tilt angle curve, the sputtering tilt angle corresponding to different materials or different thicknesses can be quickly determined. Different materials can have different stress types, and the appropriate sputtering tilt angle can be selected according to the material and thickness of the absorption layer, so as to realize the preparation of the high-density low-stress mask absorption layer.

[0065] In some embodiments of the present disclosure, the size of the predetermined tilt angle can be 10°-60°. Different tilt angles can be selected for inclined deposition at a preset angle step, for example, the angle step is 5°, and the predetermined angles selected are 5°, 10°, 15°, 20°, etc. The size of the predetermined angle can be selected in advance according to the material of the absorption layer.

[0066] In some embodiments of the present disclosure, the material of the actual absorption layer can include one of Cr, Ta, Mo, MoSi and MoTa, that is, the material of the predetermined absorption layer can include one of Cr, Ta, Mo, MoSi and MoTa.

[0067] In some embodiments of the present disclosure, the thickness of the actual absorption layer can be 38 nm ~ 42 nm, that is, the thickness of the predetermined absorption layer can be in the range of 38 nm ~ 42 nm, such as 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, and preferably 40 nm.

[0068] Embodiments of the present disclosure also provide a preparation method of a mask blank, which can include:

[0069] The absorption layer of the mask blank is prepared by using the preparation method of the absorption layer of the mask blank.

[0070] In the case that the deformation amount and / or the surface shape PV of the surface of the mask substrate meet the preset conditions, the mask blank is prepared.

[0071] The specific details of the preparation of the absorption layer of the mask blank are not repeated here. After the preparation of the absorption layer is completed, the actual stress of the absorption layer on the mask substrate and the deformation amount or the surface shape PV of the surface of the mask substrate are verified, and if the requirements are met, the mask blank with the stress and the surface shape meeting the requirements is obtained through other subsequent processing.

[0072] Embodiments of the present disclosure also provide a mask blank prepared by using the preparation method of the mask blank described above. For implementation details of the embodiments, please refer to the foregoing embodiment section, which will not be repeated here.

[0073] In order to more clearly illustrate the effectiveness of the above-mentioned preparation method of the absorption layer of the mask blank, some specific examples are given below to illustrate.

[0074] Embodiment one

[0075] In this embodiment, the stress-tilt curves of different material types are obtained under the predetermined deposition thickness.

[0076] In this embodiment, the predetermined deposition thickness of the absorption layer is set to 40 nm, and Cr, Ta and Mo are respectively used as the material of the absorption layer to deposit the absorption layer on the mask substrate. The stress-tilt curves corresponding to Cr, Ta and Mo respectively when the predetermined deposition thickness of the absorption layer is 40 nm are obtained.

[0077] The method of ion beam assisted deposition is used to deposit the absorption layer on the mask substrate, and the auxiliary gas used can include Ar or Xe.

[0078] Figure 3 The stress-tilt curves corresponding to the absorption layers formed by different types of materials under the same predetermined deposition thickness are schematically shown.

[0079] As Figure 3As shown, for the same predetermined deposition thickness, the stress-tilt curve corresponding to the absorption layer formed by different types of materials can be different; in the case where the material type forming the absorption layer is the same but the auxiliary gas used is different, the stress-tilt curve obtained can be different. With the increase of the deposition tilt angle, the stress of the absorption layer generally presents an increasing trend.

[0080] For example, for the same deposition tilt angle, the stress of the absorption layer formed by Cr is greater than that of the absorption layer formed by Mo, and the stress of the absorption layer formed by Mo is greater than that of the absorption layer formed by Ta.

[0081] For example, for the absorption layers formed by Cr and Mo, in the case of the same deposition tilt angle, the stress of the absorption layer deposited by using Xe as the auxiliary gas is greater than that of the absorption layer deposited by using Ar as the auxiliary gas. For the absorption layer formed by Ta, in the case of the same deposition tilt angle, the stress of the absorption layer deposited by using Xe as the auxiliary gas is less than that of the absorption layer deposited by using Ar as the auxiliary gas.

[0082] Based on the stress-tilt curve, the tilt angle corresponding to the predetermined stress range can be quickly and accurately selected according to the material type of the actual absorption layer and the deposition thickness of the actual absorption layer, and the actual absorption layer is deposited on the mask substrate surface at the tilt angle corresponding to the predetermined stress range, so as to accurately regulate the stress of the actual absorption layer, and further control the deformation amount and / or the surface figure PV of the mask substrate surface.

[0083] Embodiment Two

[0084] In this embodiment, in order to solve the problem of the change of the mask surface figure caused by the stress of the Cr layer (absorption layer), the appropriate sputtering tilt angle can be selected by using the results of embodiment one to reduce the stress of the film layer, and the stress values of the Cr layer deposited at different angles are measured by adjusting the relative angle between the substrate and the target material.

[0085] Table 1 shows the stress measurement values of the Cr film layer at different sputtering tilt angles.

[0086] Table 1

[0087]

[0088] Figure 4A The stress diagram of the Cr film layer at a deposition tilt angle of 60° according to the embodiment of the present disclosure is schematically shown, Figure 4B The stress diagram of the Cr film layer at a deposition tilt angle of 48° according to the embodiment of the present disclosure is schematically shown, Figure 4C The stress diagram of the Cr film layer at a deposition tilt angle of 30° according to the embodiment of the present disclosure is schematically shown, Figure 4Da stress diagram of a Cr film layer when a deposition angle is 20° according to an embodiment of the present disclosure is schematically shown, Figure 4E a stress diagram of a Cr film layer when a deposition angle is 10° according to an embodiment of the present disclosure is schematically shown.

[0089] As shown in Table 1 and Figures 4A-4E As shown in Table 1 and

[0090] Example Three

[0091] On the basis of Example One and Example Two, the same process is used to perform stress regulation on the mask substrate multiple times.

[0092] Figure 5 a stress regulation process repeatability verification result diagram of a Cr film layer according to an embodiment of the present disclosure is schematically shown.

[0093] As shown in Table 1 and Figure 5 The mask substrate absorption layer preparation method provided by the embodiment of the present disclosure has certain process stability, and the film layers prepared in different batches can meet the stress index requirement of +50 MPa~+200 MPa.

[0094] Example Four

[0095] In this embodiment, 40 nm of Cr film layer needs to be deposited on a 3-inch square quartz mask substrate as an absorption layer, and the PV variation of the central 10x10 mm area needs to be ensured to be small.

[0096] Table 2 shows the influence of the stress regulation scheme on the PV variation of the 3-inch mask surface shape before and after film plating.

[0097] Table 2

[0098]

[0099] Figure 6A a surface shape diagram of a mask substrate when a deposition angle is 60° according to an embodiment of the present disclosure is schematically shown, Figure 6B a surface shape diagram of a mask substrate when a deposition angle is 48° according to an embodiment of the present disclosure is schematically shown, Figure 6C a surface shape diagram of a mask substrate when a deposition angle is 30° according to an embodiment of the present disclosure is schematically shown, Figure 6D a surface shape diagram of a mask substrate when a deposition angle is 20° according to an embodiment of the present disclosure is schematically shown, Figure 6E a surface shape diagram of a mask substrate when a deposition angle is 10° according to an embodiment of the present disclosure is schematically shown.

[0100] As shown in Table 2 and Figures 6A-6EAs shown in Table 3, the mask plate absorption layer preparation method of the embodiment of the present disclosure suppresses the influence of Cr film layer stress on the deformation of the 3-inch mask plate, and the PV variation of the substrate before and after film plating at each angle is controlled at about 5 nm. When the deposition angle is 20°, the PV variation of the substrate can be controlled at about 3 nm, which can ensure the subsequent processing requirements.

[0101] Example Five

[0102] In this embodiment, a 6-inch square quartz mask plate substrate with a thinned center needs to deposit a 40-nm Cr absorption layer. Because the center of the substrate is relatively thin, it is necessary to ensure that the PV variation before and after film plating is small to prevent the substrate from deforming and being damaged. The film layer stress range is required to be +50 MPa ~ +200 MPa, the deposition angle range is preferably 15° ~ 25°, the actual process selects 20°, and the process gas is Ar.

[0103] Table 3 shows the influence of the above stress regulation scheme on the PV variation of the 6-inch center-thinned mask surface shape before and after film plating.

[0104] Table 3

[0105]

[0106] Figure 7A Figure 1 shows the initial surface shape of the whole 6-inch center-thinned mask substrate before film plating according to the embodiment of the present disclosure, Figure 7B Figure 2 shows the surface shape of the whole 6-inch center-thinned mask substrate after film plating according to the embodiment of the present disclosure. Figure 8A Figure 3 shows the initial surface shape of the 26 mm×33 mm standard field of the 6-inch center-thinned mask substrate before film plating according to the embodiment of the present disclosure, Figure 8B Figure 4 shows the surface shape of the 26 mm×33 mm standard field of the 6-inch center-thinned mask substrate after film plating according to the embodiment of the present disclosure.

[0107] As shown in Table 3, Figure 7A , Figure 7B , Figure 8A , Figure 8B As shown in Table 3, the mask plate absorption layer preparation method of the embodiment of the present disclosure suppresses the deformation of the 6-inch center-thinned mask plate caused by the Cr film layer stress, the PV variation of the whole substrate before and after film plating is controlled at about 20 nm, and the PV of the 26 mm×33 mm standard field in the front center can be controlled at about 2 nm. The influence of the absorption layer deposition step on the position error accuracy of the mask plate and the line width uniformity of the high-resolution pattern is reduced to be negligible.

[0108] In summary, the experimental data fully verify that the sputtering at the inclination angle can effectively reduce the stress of the Cr film layer and reduce the mask surface shape change caused by the stress of the Cr film layer, thereby providing a good foundation for the mask straight writing pattern position error, CDU control and other technical indicators.

[0109] The specific embodiments described above further illustrate the objects, technical solutions, and advantages of the present disclosure. It should be understood that the above are only preferred embodiments of the present disclosure and the technical principles used. Those skilled in the art will understand that the present disclosure is not limited to the specific embodiments described herein. Various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of the present disclosure. Therefore, although the present disclosure has been described in detail through the above embodiments, the present disclosure is not limited to the above embodiments. Without departing from the concept of the present disclosure, more other equivalent embodiments can also be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a mask absorption layer, characterized in that, include: Obtain the mask substrate; An actual absorption layer is prepared on the surface of the mask substrate by ion beam deposition. The stress of the actual absorption layer is controlled by adjusting the angle between the incident direction of the target particles required to prepare the actual absorption layer and the direction perpendicular to the surface of the mask substrate, and by changing the relative angle between the mask substrate and the target material during ion beam deposition. The deformation and / or surface shape PV of the mask substrate surface are also controlled. The method of adjusting the angle between the incident direction of the target particles required for preparing the absorption layer and the surface of the mask substrate by changing the relative angle between the mask substrate and the target material during ion beam deposition includes: Based on the stress-tilt curve, according to the material type and deposition thickness of the actual absorption layer, the tilt angle corresponding to a predetermined stress range is selected and the actual absorption layer is deposited on the surface of the mask substrate at the tilt angle corresponding to the predetermined stress range to form the actual absorption layer. The stress-tilt curves include stress-tilt curves of predetermined absorber layers with different deposition thicknesses under different material types, or stress-tilt curves of predetermined absorber layers of different material types under different deposition thicknesses.

2. The method according to claim 1, characterized in that, Also includes: Obtain the first surface profile of a mask substrate on which no predetermined absorption layer is formed; By preparing predetermined absorption layers of different predetermined deposition thicknesses on the mask substrate at multiple predetermined relative angles, the second surface shape of the mask substrate with predetermined absorption layers of various predetermined deposition thicknesses is obtained. The stress on the mask substrate surface of the predetermined absorption layer with a predetermined deposition thickness is calculated based on the change in surface curvature between the second surface shape and the first surface shape corresponding to each predetermined deposition thickness of the predetermined absorption layer. For multiple predetermined relative angles, the stress magnitude on the surface of the mask substrate is fitted to the predetermined absorption layer with a predetermined deposition thickness at each predetermined deposition thickness to form stress-tilt angle curves corresponding to the predetermined absorption layer with different deposition thicknesses. Repeat the above steps to obtain stress-tilt curves of the predetermined absorption layer of different material types at different deposition thicknesses.

3. The method according to claim 1, characterized in that, Also includes: Obtain the first surface profile of a mask substrate on which no predetermined absorption layer is formed; By preparing predetermined absorption layers of different material types on the mask substrate at multiple predetermined relative angles, the second surface shape of the mask substrate with predetermined absorption layers of various predetermined material types formed on its surface is obtained; The stress on the surface of the mask substrate is calculated based on the change in surface curvature between the second surface shape and the first surface shape of the predetermined absorption layer corresponding to each predetermined material type. For multiple predetermined relative angles, the stress magnitude of the predetermined absorption layer of each predetermined material type on the surface of the mask substrate is fitted to form stress-tilt angle curves corresponding to the predetermined absorption layer of different material types. Repeat the above operation to obtain stress-tilt curves of the predetermined absorption layer with different deposition thicknesses under different material types.

4. The method according to claim 2 or 3, characterized in that, The material of the actual absorber layer includes one of Cr, Ta, Mo, MoSi, and MoTa.

5. The method according to claim 2 or 3, characterized in that, The actual absorption layer has a thickness of 38 nm to 42 nm.

6. The method according to claim 2 or 3, characterized in that, The predetermined relative angle is between 10° and 60°.

7. The method according to any one of claims 1-3, characterized in that, The mask substrate is made of materials including sapphire or fused silica.

8. A method for preparing a photomask, characterized in that, The absorption layer of the mask is prepared using the preparation method according to any one of claims 1-7; A mask is prepared when the deformation and / or surface shape PV on the surface of the mask substrate meets preset conditions.

9. A photomask, characterized in that, The mask is prepared using the preparation method described in claim 8.

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