Mask absorption layer preparation method, mask and preparation method thereof

Abstract

The invention provides a preparation method of a mask plate absorption layer, a mask plate and a preparation method thereof, and relates to the technical field of photoetching, and the preparation method of the mask plate absorption layer comprises the following steps: obtaining a mask substrate; preparing a transition film layer on the surface of the mask substrate, and preparing an actual absorption layer on the surface of the transition film layer; wherein the transition film layer is used for counteracting the stress of the actual absorption layer on the surface of the mask substrate so as to control the deformation quantity and / or the surface shape PV of the surface of the mask substrate.

Description

Technical Field

[0001] The present disclosure relates to the field of photolithography technology, and in particular to a method for preparing a mask absorption layer, a mask and a method for preparing the same. Background Art

[0002] In the manufacturing process of micro-nano lithography masks, the deposition of the absorption layer is a very important step and the basis for mask pattern processing. In practical applications, the absorption layer material deposited on the mask substrate often has a certain residual stress. If the residual stress of the absorption layer material is large, the mask substrate will be deformed, thereby increasing the position error and line width non-uniformity of the mask pattern processing, which will have an adverse effect on the lithography process. Summary of the invention

[0003] In view of this, the first aspect of the embodiments of the present disclosure provides a method for preparing a mask plate absorption layer to obtain a mask substrate; prepare a transition film layer on the surface of the mask substrate, and prepare an actual absorption layer on the surface of the transition film layer; wherein the transition film layer is used to offset the stress of the actual absorption layer on the surface of the mask substrate, so as to control the deformation amount and / or surface shape PV of the mask substrate surface.

[0004] According to an embodiment of the present disclosure, the method also includes: obtaining a first surface shape of a mask substrate whose surface is not provided with a predetermined absorption layer; preparing different types of predetermined absorption layers on the mask substrate to obtain second surface shapes of mask substrates whose surfaces are provided with various types of predetermined absorption layers; calculating the stress of the corresponding type of predetermined absorption layer on the surface of the mask substrate according to the change in surface curvature between the second surface shape corresponding to the various types of predetermined absorption layers and the first surface shape; determining the first stress type of the various types of predetermined absorption layers on the surface of the mask substrate and the second stress type of the transition film layer required for the various types of predetermined absorption layers according to the stress size of the various types of predetermined absorption layers on the surface of the mask substrate, wherein the first stress type of the predetermined absorption layer on the surface of the mask substrate is opposite to the second stress type of the transition film layer required for the predetermined absorption layer.

[0005] According to an embodiment of the present disclosure, a transition film layer is prepared on the surface of a mask substrate, including: determining an actual absorption layer and a first stress type of the actual absorption layer on the surface of the mask substrate from various types of predetermined absorption layers; obtaining a second stress type of the transition film layer required for the actual absorption layer based on the first stress type as a target stress type; and preparing a transition film layer having a stress type of the target stress type on the surface of the mask substrate.

[0006] According to an embodiment of the present disclosure, a transition film layer with a stress type of a target stress type is prepared on a surface of a mask substrate, including: determining a predetermined etching selectivity range between an actual absorption layer and the transition film layer of the target stress type, wherein the predetermined etching selectivity range should satisfy that the transition film layer of the target stress type can serve as a hard mask layer for the actual absorption layer; selecting a transition film layer with a stress type of the target stress type based on the predetermined etching selectivity range and preparing the transition film layer with a stress type of the target stress type on the surface of the mask substrate.

[0007] According to an embodiment of the present disclosure, a transition film layer is prepared on a mask substrate, including: when the first stress type of the actual absorption layer on the surface of the mask substrate is compressive stress, a transition film layer whose second stress type is tensile stress is prepared on the mask substrate; or, when the first stress type of the actual absorption layer on the surface of the mask substrate is tensile stress, a transition film layer whose second stress type is compressive stress is prepared on the mask substrate.

[0008] According to an embodiment of the present disclosure, the transmittance of the transition film layer in the application band is greater than 80%.

[0009] According to an embodiment of the present disclosure, the material of the actual absorption layer includes at least one of Cr, Ta, and Mo, and the material of the transition film layer includes at least one of SiO2, Si, and TiO2. The thickness of the transition film layer is 90 nm to 100 nm, and the thickness of the actual absorption layer is 38 nm to 42 nm.

[0010] According to an embodiment of the present disclosure, the deposition process of the transition film layer includes at least one of chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition and ion beam deposition.

[0011] A second aspect of the disclosed embodiments provides a method for preparing a mask, wherein the absorption layer of the mask is prepared by the above-mentioned preparation method; when the deformation amount and / or surface shape PV of the mask substrate surface meets preset conditions, the mask is prepared.

[0012] A third aspect of the embodiments of the present disclosure provides a mask, which is prepared by the above-mentioned preparation method.

[0013] The mask absorption layer preparation method, mask and preparation method thereof provided by the embodiments of the present disclosure have at least the following technical effects:

[0014] Before preparing the absorption layer on the mask substrate, a transition film layer is prepared in advance, and then the absorption layer is prepared on the transition film layer. The transition film layer offsets the influence of the absorption layer stress on the mask surface shape, thereby greatly reducing the change in the mask surface shape before and after the absorption layer is coated.

[0015] This method is universal and is not limited to the regulation of mask absorption layer stress and mask surface shape control. For a wider range of substrate deformation control needs, this method can also be applied to select corresponding regulatory film layers with appropriate stress types and values ​​for surface shape control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1 The flowchart of the method for preparing the mask absorption layer according to the embodiment of the present disclosure is schematically shown.

[0018] Figure 2 The schematic diagram shows the structure corresponding to the preparation of the mask absorption layer by the existing method and the structure schematic diagram showing the preparation of the mask absorption layer by the preparation method of the embodiment of the present disclosure.

[0019] Figure 3A The stress diagram of the Cr film layer prepared by conventional RF sputtering is schematically shown.

[0020] Figure 3B The stress diagram of the Cr film layer prepared by the preparation method of the embodiment of the present disclosure is schematically shown.

[0021] Figure 4 The diagram schematically shows the result of repeatability verification of the Cr film stress control process according to an embodiment of the present disclosure.

[0022] Figure 5 A diagram schematically shows a comparison of the suppression effect of the stress control scheme according to an embodiment of the present disclosure on the PV increment of the mask surface before and after coating.

[0023] Figure 6 The diagram schematically shows the surface measurement result of a 6mm×6mm graphic area at the center of the front side of the mask after adopting the stress control method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0025] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components. All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] In the process of realizing the present disclosure, it was found that the metal chromium (Cr) layer is often used as the absorption layer material of the photomask due to its high absorption rate of ultraviolet light. Usually, in order to facilitate the pattern processing of the mask, it is required to make the thickness of the Cr film as thin as possible while ensuring that the ultraviolet light transmittance is lower than a certain value, which requires the density of the prepared Cr film to be as high as possible. In order to improve the density of the Cr film, the Cr film is usually prepared by radio frequency sputtering, and the Cr film prepared in this way usually has a very high residual stress, which will cause a large deformation of the substrate and cause damage to the position error control and pattern uniformity of the mask.

[0027] The residual stress of the chromium film prepared by magnetron sputtering can be reduced by increasing the sputtering chamber pressure, using a DC power supply for sputtering, post-annealing, etc. However, these methods have a limited range of adjustment for the stress value and will lead to a decrease in the density of the plated chromium layer, which will lead to an increase in the transmittance of the chromium layer of the required thickness under incident light of a specific wavelength, as well as an increase in surface roughness, reducing its excellent performance as a photomask absorption layer.

[0028] In view of this, the embodiments of the present disclosure aim to provide a method for preparing a mask absorption layer, a mask and a method for preparing the same, which, under the premise of ensuring that the absorption rate of the absorption layer remains unchanged, reduces the influence of the stress of the absorption layer on the deformation of the mask substrate before and after coating, and provides a new technical route for effectively suppressing the influence of the stress of the absorption layer on the surface shape of the mask substrate. The following is a detailed introduction in conjunction with specific embodiments.

[0029] Figure 1 The flowchart of the method for preparing the mask absorption layer according to the embodiment of the present disclosure is schematically shown.

[0030] like Figure 1 As shown, the method for preparing a mask absorption layer in this embodiment may include operations S110 to S120.

[0031] In operation S110, a mask substrate is obtained.

[0032] In operation S120, a transition film layer is prepared on the mask substrate, and an actual absorption layer is prepared on the transition film layer. The transition film layer is used to offset the stress of the actual absorption layer on the surface of the mask substrate to control the deformation amount of the surface of the mask substrate.

[0033] In some embodiments of the present disclosure, the mask substrate may include, for example, sapphire or fused quartz of any surface shape. The specific type of the mask substrate may be selected according to actual application requirements, and the present disclosure does not limit it. The actual absorption layer may be understood as the absorption layer that needs to be prepared in the process of preparing the finished mask.

[0034] In some embodiments of the present disclosure, the first stress type of the transition film layer and the second stress type of the actual absorption layer may be opposite, and the stress magnitude of the transition film layer and the stress magnitude of the absorption layer may be comparable.

[0035] Based on this, before preparing the finished mask, it is necessary to predetermine the required transition film layers corresponding to the absorption layers of various stress types. As a possible implementation, determining the required transition film layers corresponding to the absorption layers of various stress types may include:

[0036] A first surface shape of the mask substrate having no predetermined absorption layer formed on the surface is obtained.

[0037] Different types of predetermined absorption layers are prepared on the mask substrate to obtain respective second surface shapes of the mask substrates with the various types of predetermined absorption layers formed on the surface.

[0038] The stress magnitude of the corresponding type of predetermined absorption layer on the surface of the mask substrate is calculated according to the surface curvature variation between the second surface shape and the first surface shape corresponding to each type of predetermined absorption layer.

[0039] According to the stress magnitudes of various types of predetermined absorption layers on the surface of the mask substrate, the first stress types of various types of predetermined absorption layers on the surface of the mask substrate and the second stress types of transition film layers required for various types of predetermined absorption layers are determined, wherein the first stress type of the predetermined absorption layer on the surface of the mask substrate is opposite to the second stress type of the transition film layer required for the predetermined absorption layer.

[0040] For example, various types of predetermined absorption layers are plated on the mask substrate, and the surface shape of the mask is measured with a stress meter before and after the coating. The stress meter will calculate the type and magnitude of stress of the plated predetermined absorption layer on the substrate according to the change in the curvature of the mask surface shape before and after the coating. If the stress value calculated by the stress meter is a positive value, it can be indicated that the stress of the plated predetermined absorption layer on the mask substrate is compressive stress; if the stress value calculated by the stress meter is a negative value, it can be indicated that the stress of the plated predetermined absorption layer on the substrate is tensile stress. The predetermined absorption layer can be understood as the absorption layer that needs to be prepared in the process of predetermining the absorption layer of various stress types corresponding to the required transition film layer.

[0041] In some embodiments of the present disclosure, preparing a transition film layer on a mask substrate may include:

[0042] An actual absorption layer and a first stress type of the actual absorption layer on the surface of the mask substrate are determined from various types of predetermined absorption layers.

[0043] A second stress type of the transition film layer required by the actual absorption layer is obtained based on the first stress type as the target stress type.

[0044] A transition film layer having a stress type of a target stress type is prepared on the surface of the mask substrate.

[0045] Furthermore, a transition film layer having a stress type of a target stress type is prepared on the surface of a mask substrate, including: determining a predetermined etching selectivity range between the actual absorption layer and the transition film layer having a target stress type, wherein the predetermined etching selectivity range should satisfy that the transition film layer having the target stress type can serve as a hard mask layer for the actual absorption layer; selecting a transition film layer having a stress type of the target stress type based on the predetermined etching selectivity range and preparing the transition film layer having the stress type of the target stress type on the surface of the mask substrate.

[0046] Since the etching selectivity ratio between the actual absorption layer and the transition film layer is considered when preparing the transition film layer, the transition layer can be used as a hard mask layer of the actual absorption layer, thereby achieving high-quality transfer of the actual absorption layer.

[0047] In some embodiments of the present disclosure, preparing a transition film layer on a mask substrate may include:

[0048] In the case that the first stress type of the actual absorption layer on the surface of the mask substrate is compressive stress, a transition film layer whose second stress type is tensile stress is prepared on the mask substrate.

[0049] According to an embodiment of the present disclosure, the first stress type of the predetermined absorption layer on the surface of the mask substrate is opposite to the second stress type of the transition film layer required by the predetermined absorption layer. It can be understood that if the first stress type is compressive stress, the second stress type can be tensile stress, or if the first stress type is tensile stress, the second stress type can be compressive stress. Based on this, in some other embodiments of the present disclosure, preparing the transition film layer on the mask substrate may further include:

[0050] When the first stress type of the actual absorption layer on the surface of the mask substrate is tensile stress, a transition film layer whose second stress type is compressive stress is prepared on the mask substrate.

[0051] As a possible implementation manner, the material of the absorption layer may include at least one of Cr, Ta, and Mo, and the material of the transition film layer may include at least one of SiO2, Si, and TiO2.

[0052] Figure 2 The schematic diagram shows the structure corresponding to the preparation of the mask absorption layer by the existing method and the structure schematic diagram showing the preparation of the mask absorption layer by the preparation method of the embodiment of the present disclosure.

[0053] like Figure 2 As shown in the figure, taking the Cr film layer as the actual absorption layer as an example, based on the predetermined absorption layers of various stress types corresponding to the required transition film layer, a SiO2 film layer with a stress type opposite to that of the Cr film layer, a stress value that can offset that of the Cr film layer, and a high transmittance at the used band (e.g., 365 nm) can be selected as the transition film layer to regulate the stress of the Cr film layer without affecting the transmittance performance of the mask. After the SiO2 film layer is pre-deposited and then the Cr film layer is prepared, the SiO2 film layer can offset the stress of the Cr film layer on the mask substrate and reduce the change in the mask surface shape before and after the Cr film layer is coated.

[0054] Taking the Mo film layer as the actual absorption layer as an example, based on the predetermined various stress types of the absorption layer corresponding to the required transition film layer, a Si film layer with a stress type opposite to that of the Mo film layer, a stress value that can offset the Mo film layer and a high transmittance in the used band (for example, 193 nm) can be selected to regulate the stress of the Mo film layer.

[0055] During the preparation process, a transition film layer can be first deposited on the surface of the mask substrate, and then the required actual absorption layer can be deposited after cooling.

[0056] In some embodiments of the present disclosure, the transmittance of the transition film layer in the applied wavelength band may be greater than 80% to ensure better transmission of light in the used wavelength band.

[0057] In some embodiments of the present disclosure, the deposition process and thickness of the transition film layer can be controlled to adjust the stress of the absorption layer material to a desired range, thereby suppressing the influence of the absorption layer stress on the mask surface shape.

[0058] As a possible implementation, the thickness of the transition film layer may be 90 nm to 100 nm, and the thickness of the actual absorption layer may be 38 nm to 42 nm.

[0059] As another possible implementation, the deposition process of the transition film layer includes at least one of chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition and ion beam deposition.

[0060] The embodiment of the present disclosure also provides a method for preparing a mask, which may include:

[0061] The absorption layer of the mask is prepared by adopting the method for preparing the absorption layer of the mask.

[0062] When the deformation amount and / or the surface shape PV of the mask substrate surface meets the preset conditions, the mask plate is prepared.

[0063] The specific details of preparing the absorption layer of the mask are not described here. After the preparation of the absorption layer is completed, the actual stress of the absorption layer on the mask substrate and the surface deformation or surface shape PV of the mask substrate are verified. If they meet the requirements, other subsequent processing is performed to obtain a mask that meets the requirements in terms of stress and surface shape.

[0064] An embodiment of the present disclosure further provides a mask, which is prepared using the above-mentioned mask preparation method, and the specific details are not repeated here.

[0065] In order to more clearly illustrate the effectiveness of the above-mentioned method for preparing the mask absorption layer and the method for preparing the mask, some specific examples are given below for illustration.

[0066] Embodiment 1

[0067] In this embodiment, a Cr film layer with a thickness of 40 nm may be deposited on the surface of a 6-inch square photomask as an absorption layer.

[0068] In order to solve the problem of mask shape change caused by Cr film stress, the SiO2 layer prepared by chemical vapor deposition can be selected as the regulating layer, that is: before depositing the Cr film, a SiO2 film with a thickness of 100 nm is deposited on the substrate by chemical vapor deposition as a transition film layer. The stress value of the plated SiO2 film is -1000 MPa tested by a stress meter. After the substrate is cooled, the substrate is placed in the chamber of the RF sputtering deposition device, and a Cr film with a thickness of 40 nm is continued to be plated on the SiO2 film layer. The stress value of the Cr film is measured after it is taken out.

[0069] Figure 3A The stress diagram of the Cr film layer prepared by conventional RF sputtering is schematically shown. Figure 3B The stress diagram of the Cr film layer prepared by the preparation method of the embodiment of the present disclosure is schematically shown.

[0070] like Figure 3A and 3B As shown in the figure, the stress value of the Cr film layer with higher density prepared by radio frequency sputtering is +1800MPa. After regulation, the stress value of the Cr layer is reduced to +140 MPa, meeting the stress index requirements of +50 MPa~+200 MPa.

[0071] Embodiment 2

[0072] On the basis of the first embodiment, the same process is used to perform stress control on the mask substrate for multiple times.

[0073] Figure 4 The diagram schematically shows the result of repeatability verification of the Cr film stress control process according to an embodiment of the present disclosure.

[0074] like Figure 4 As shown, the method for preparing the mask absorption layer provided in the embodiment of the present disclosure has a certain process stability, and the film layers prepared in different batches can meet the stress index requirements of +50 MPa~+200 MPa.

[0075] Embodiment 3

[0076] Based on the first embodiment, an experiment was conducted on a 6-inch square quartz mask substrate with bosses. Figure 5 A schematic diagram shows a comparison of the suppression effect of the stress control scheme according to an embodiment of the present disclosure on the PV increment of the mask surface before and after coating. Figure 6 The figure schematically shows the surface shape measurement result of a 6mm×6mm graphic area at the center of the front side of the mask after adopting the stress control method according to an embodiment of the present disclosure.

[0077] like Figure 5 and Figure 6 As shown in the figure, the PV value of the front and back profile before and after coating increases by more than 500 nm, which has an adverse effect on the position error accuracy control of the mask and the line width uniformity control of high-resolution graphics. After using the method disclosed in the present invention for regulation, the results show that the stress regulation scheme disclosed in the present invention suppresses the deformation of the 6-inch mask caused by the stress of the Cr film layer, and the PV increment of the substrate before and after coating is reduced from 500 nm to 100 nm ( Figure 5 ), the PV of the 6mm×6mm boss surface on the front side can be controlled to be around 4 nm ( Figure 6 ). The influence of the absorption layer deposition step on the position error accuracy of the mask and the line width uniformity of the high-resolution pattern is reduced to a negligible level.

[0078] In summary, the above experimental data fully verify that the stress control scheme disclosed in the present invention can effectively reduce the stress of the Cr film layer and reduce the change of the mask surface shape caused by the stress of the Cr film layer, providing a good foundation for technical indicators such as the direct writing pattern position error of the mask and CDU control.

[0079] The embodiments of the present disclosure are described above. However, these embodiments are only for the purpose of illustration and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for preparing a mask absorption layer, characterized in that: include: obtaining a mask substrate; A transition film layer is prepared on the surface of the mask substrate, and an actual absorption layer is prepared on the surface of the transition film layer; wherein the transition film layer is used to offset the stress of the actual absorption layer on the surface of the mask substrate to control the deformation amount and / or surface shape PV of the surface of the mask substrate.

2. The method according to claim 1, characterized in that Also includes: Obtaining a first surface shape of a mask substrate having no predetermined absorption layer formed on the surface; Preparing different types of predetermined absorption layers on the mask substrate to obtain respective second surface shapes of the mask substrates with the various types of predetermined absorption layers formed on the surface; Calculating the stress of the corresponding type of predetermined absorption layer on the surface of the mask substrate according to the curvature variation between the second surface shape corresponding to each type of predetermined absorption layer and the first surface shape; According to the stress magnitudes of various types of predetermined absorption layers on the surface of the mask substrate, the first stress types of various types of predetermined absorption layers on the surface of the mask substrate and the second stress types of transition film layers required for various types of predetermined absorption layers are determined, wherein the first stress type of the predetermined absorption layer on the surface of the mask substrate is opposite to the second stress type of the transition film layer required for the predetermined absorption layer.

3. The method according to claim 2, characterized in that The step of preparing a transition film layer on the surface of the mask substrate comprises: Determine the actual absorption layer and the first stress type of the actual absorption layer on the surface of the mask substrate from various types of predetermined absorption layers; obtain the second stress type of the transition film layer required for the actual absorption layer as the target stress type based on the first stress type; A transition film layer having a stress type of the target stress type is prepared on the surface of the mask substrate.

4. The method according to claim 3, characterized in that The step of preparing a transition film layer having a stress type of the target stress type on the surface of the mask substrate comprises: Determining a predetermined etching selectivity range between the actual absorption layer and the transition film layer of the target stress type, wherein the predetermined etching selectivity range should satisfy that the transition film layer of the target stress type can serve as a hard mask layer of the actual absorption layer; A transition film layer whose stress type is the target stress type is selected based on the predetermined etching selectivity range, and the transition film layer whose stress type is the target stress type is prepared on the surface of the mask substrate.

5. The method according to claim 1 or 2, characterized in that: The step of preparing a transition film layer on the mask substrate comprises: In the case where the first stress type of the actual absorption layer on the surface of the mask substrate is compressive stress, a transition film layer whose second stress type is tensile stress is prepared on the mask substrate; Alternatively, when the first stress type of the actual absorption layer on the surface of the mask substrate is tensile stress, a transition film layer whose second stress type is compressive stress is prepared on the mask substrate.

6. The method according to claim 1 or 2, characterized in that: The transmittance of the transition film layer in the application band is greater than 80%.

7. The method according to claim 1 or 2, characterized in that: The material of the actual absorption layer includes at least one of Cr, Ta, and Mo, and the material of the transition film layer includes at least one of SiO2, Si, and TiO2; The thickness of the transition film layer is 90 nm to 100 nm, and the thickness of the actual absorption layer is 38 nm to 42 nm.

8. The method according to claim 1 or 2, characterized in that: The deposition process of the transition film layer includes at least one of chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition and ion beam deposition.

9. A method for preparing a mask, characterized in that: The absorption layer of the mask is prepared by the preparation method according to any one of claims 1 to 8; When the deformation amount and / or the surface shape PV of the mask substrate surface meets the preset conditions, the mask plate is prepared.

10. A mask, characterized in that: The mask is prepared by the preparation method according to claim 9.

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