Repair method for surface defects of mask plate

Abstract

The invention provides a method for repairing surface defects of a mask plate, which comprises the following steps of: coating a photosensitive material on the front surface of the mask plate to form a photosensitive layer; based on the layout of the mask plate, irradiating the mask plate from the back surface of the mask plate, so that light rays penetrate through the area where the mask layer defects of the mask plate are located, and exposing the photosensitive material in the area where the mask layer defects are located; developing the photosensitive layer, and removing the photosensitive material in the defect area of the mask; depositing a masking material on the front surface of the mask plate, wherein the masking material fills the area where the masking layer defect of the mask plate is located; and cleaning after removing the photosensitive layer to obtain the mask plate after the defect of the masking layer is repaired. According to the method, the defects of the masking layer on the surface of the mask plate can be repaired, the defects of the mask plate are reduced, the service life of the mask plate is prolonged, and the repair efficiency of the mask plate is improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of photolithography, and more particularly to a method for repairing surface defects of a super-resolution imaging photomask. BACKGROUND

[0002] For a conventional projection imaging optical photolithography system, evanescent waves carrying sub-wavelength information of a mask pattern cannot participate in imaging, resulting in a 1 / 4 wavelength linewidth resolution limit. The main principle of surface plasmon (SP) super-resolution imaging photolithography is to use a nano-metal imaging film layer structure such as a superlens to excite SP modes in a wide spatial frequency spectrum range and enhance the intensity of evanescent waves carrying high-frequency spatial information, and to realize the transfer of mask patterns to a photoresist space and super-resolution imaging photolithography by means of negative refraction imaging effect.

[0003] SP super-resolution imaging photolithography has high pattern resolution, but has shallow focal depth, short working distance, and the distance between the mask and the exposure wafer needs to be controlled within the nanometer range, resulting in the need to adopt a close or even contact photolithography mode in SP super-resolution imaging photolithography experiments. The surface of the SP super-resolution imaging photomask has no protective film for protection. When the mask or wafer surface is contaminated with particles and the particles are relatively hard, the particles may crush the mask layer on the surface of the mask during the bonding of the mask and the wafer, thereby causing damage to the mask layer. After the mask layer of the mask is damaged, the light-shielding area becomes a light-transmitting area, thereby affecting the exposure result and forming a fixed defect.

[0004] When the mask layer of the super-resolution imaging photomask is damaged, a common method is to use a focused ion beam (FIB) for repair. However, the gallium (Ga+) ions commonly used by FIB may be embedded in the mask plate material (such as quartz or chromium), resulting in unintended changes in light transmission or scattering. In addition, the deposition material (such as platinum or carbon) is often used to fill the defects in FIB repair, but the optical properties (refractive index, absorption rate) of the deposition material may not match the original material of the mask plate, and the ideal repair effect cannot be achieved. At the same time, FIB repair is a serial process that requires point-by-point scanning for deposition or etching. For larger defects or high-precision repair situations, it takes a very long time and affects the repair efficiency. SUMMARY

[0005] Therefore, the present disclosure provides a method for repairing surface defects of a mask plate, which can at least partially solve the above technical problems.

[0006] The embodiment of the present disclosure provides a mask plate surface mask layer defect repairing method, which comprises the following steps: coating a photosensitive material on the front surface of a mask plate to form a photosensitive layer; irradiating the mask plate from the back surface of the mask plate, so that the light passes through the area where the mask layer defect is located, and the photosensitive material in the area where the mask layer defect is located is exposed; developing the photosensitive layer to remove the photosensitive material in the area where the mask layer defect of the mask plate is located; depositing a mask material on the front surface of the mask plate, and the mask material fills the area where the mask layer defect of the mask plate is located; and cleaning after removing the photosensitive layer to obtain the mask plate after the mask layer defect is repaired.

[0007] According to the embodiment of the present disclosure, the mask plate comprises a substrate and a mask layer formed on the surface of the substrate; the substrate comprises one of a quartz substrate, a glass substrate, a sapphire substrate and an organic thin film substrate.

[0008] According to the embodiment of the present disclosure, the step of coating a photosensitive material on the front surface of the mask plate to form a photosensitive layer comprises the following steps: coating one of ultraviolet photoresist, electron beam photoresist and PMMA series photoresist on the front surface of the mask plate to form a photosensitive layer.

[0009] According to the embodiment of the present disclosure, the photosensitive layer with a thickness of 30nm to 500nm is formed on the front surface of the mask plate.

[0010] According to the embodiment of the present disclosure, the step of irradiating the mask plate from the back surface of the mask plate, so that the light passes through the area where the mask layer defect is located, and the photosensitive material in the area where the mask layer defect is located is exposed comprises the following steps: using a super-resolution imaging lithography, electron beam direct writing lithography, laser direct writing lithography or projection lithography method to expose the photosensitive material in the area where the mask layer defect is located.

[0011] According to the embodiment of the present disclosure, the step of developing the photosensitive layer comprises the following steps: soaking the mask plate comprising the exposed photosensitive layer in a developing solution for development, or spraying the developing solution on the photosensitive layer of the mask plate for development; wherein the developing solution does not damage the mask layer of the mask plate.

[0012] According to the embodiment of the present disclosure, the step of depositing a mask material on the front surface of the mask plate comprises the following steps: depositing the mask material on the front surface of the mask plate by using evaporation deposition, magnetron sputtering deposition, atomic layer deposition or chemical vapor deposition, wherein the thickness of the film layer formed by the mask material is the same as the thickness of the mask layer, and the mask material is the same as the material of the mask layer.

[0013] According to the embodiment of the present disclosure, the mask material with a thickness of 10nm to 500nm is deposited on the front surface of the mask plate.

[0014] According to an embodiment of the present disclosure, the removing the photoresist layer comprises: removing the photoresist layer by dry etching or wet etching, wherein the dry etching comprises one of reactive ion etching and inductively coupled plasma etching, and the wet etching comprises etching by using at least one of a stripping liquid, acetone and ethanol.

[0015] According to an embodiment of the present disclosure, the cleaning comprises: cleaning the mask after removing the photoresist layer by dry cleaning or wet cleaning; the dry cleaning comprises at least one of ultraviolet ozone, supercritical CO2 cleaning and oxygen plasma etching; and the wet cleaning comprises cleaning by using at least one of acetone, ethanol, a mixture of sulfuric acid and hydrogen peroxide and an alkaline cleaning agent.

[0016] The mask surface defect repairing method provided by the embodiments of the present disclosure has at least the following technical effects.

[0017] Since the area where the mask layer defect is located can be transparent, the mask is irradiated from the back surface of the mask, the light passes through the area where the mask layer defect is located, the photosensitive material corresponding to the area where the mask layer defect is located is exposed, and the photosensitive material in the area where the mask layer defect is located can be removed through subsequent development, so that the mask layer defect can be repaired by depositing a mask material in the area where the mask layer defect is located.

[0018] The method repairs the damage defects of the mask layer of the super-resolution imaging photolithography mask by coating, photolithography, development and film plating processes, and the repair material is the same as the material of the mask layer of the mask, so that the optical properties of the deposited material are not different, the problems of the traditional FIB mask repair are solved, and the repair of the damage defects of the mask layer is completed in parallel, which greatly improves the repair efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] 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 with reference to the accompanying drawings.

[0020] Figure 1 A flowchart of a super-resolution imaging photolithography mask surface defect repairing method according to an embodiment of the present disclosure is schematically shown.

[0021] Figure 2 Cross-sectional structure diagrams corresponding to each stage in the repairing process of the super-resolution imaging photolithography mask surface defect according to an embodiment of the present disclosure are schematically shown. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it would be apparent to those skilled in the art that the present disclosure can be practiced without these specific details. In other instances, well-known structures and techniques have been described in detail in order to avoid obscuring the concepts of the present disclosure.

[0023] The present disclosure provides a mask plate surface defect repair method, which can repair defects of a masking layer, reduce defects of a mask plate, improve the service life of the mask plate, and improve mask repair efficiency by using gluing, photolithography, developing, and film plating processes. Details are described below.

[0024] Figure 1 A flowchart of a mask plate surface defect repair method according to an embodiment of the present disclosure is schematically shown.

[0025] As shown in Figure 1 The mask plate surface defect repair method of the present embodiment can include operations S110-S150.

[0026] In operation S110, a photosensitive material is coated on the front surface of the mask plate to form a photosensitive layer.

[0027] In operation S120, the mask plate is irradiated from the back surface, so that the light passes through the area where the defect of the masking layer is located, and the photosensitive material in the area where the defect of the masking layer is located is exposed.

[0028] In operation S130, the photosensitive layer is developed to remove the photosensitive material in the area where the defect of the mask plate is located.

[0029] In operation S140, a masking material is deposited on the front surface of the mask plate, and the masking material fills the area where the defect of the masking layer of the mask plate is located.

[0030] In operation S150, the photosensitive layer is removed and cleaned to obtain the mask plate after the defect of the masking layer is repaired.

[0031] According to an embodiment of the present disclosure, the front surface of the mask plate refers to the surface on which the pattern layer is formed, and the back surface refers to the surface on which the pattern layer is not formed.

[0032] According to an embodiment of the present disclosure, the method can repair the non-graphic area and the graphic area of the masking layer. Since the size of the non-graphic area is much larger than that of the graphic area, and the size of the graphic area is relatively small, the process parameters for exposure in the repair process are different.

[0033] The non-patterned region and the patterned region on the mask layer can be determined based on a layout of the mask. The layout of the mask can be a layout file used to guide the geometry of the photolithography process, which defines the structure, size and positional relationship of each layer of the mask in detail.

[0034] For the non-patterned region, the defect position (e.g. particle contamination, uneven film layer or scratch) can be accurately identified based on the layout of the mask. During exposure, light is incident from the back side (e.g. the transparent substrate side) of the mask, and reaches the front film layer after passing through the transparent substrate. Since the front patterned region (e.g. chrome plating layer or phase shift layer) is not transparent to light, the light can only irradiate the non-patterned region (i.e. the transparent part without chrome layer coverage). Based on this method, the film defects in the non-patterned region can be exposed specifically, which facilitates subsequent targeted repair.

[0035] According to embodiments of the present disclosure, the mask can include a super-resolution imaging photomask.

[0036] In some embodiments, the mask includes a substrate and a mask layer formed on the surface of the substrate. The substrate includes one of a quartz substrate, a glass substrate, a sapphire substrate and an organic thin film substrate. The material forming the mask layer can be Cr, Mo or other hard metals.

[0037] In some embodiments, a photosensitive layer is formed on the front side of the mask by coating one of ultraviolet photoresist, electron beam photoresist and PMMA series photoresist on the front side of the mask.

[0038] Further, the photosensitive layer with a thickness of 30 nm to 500 nm is formed on the front side of the mask.

[0039] In some embodiments, the mask is irradiated from the back side, and the light passes through the area where the mask layer defect is located to expose the photosensitive material corresponding to the area where the mask layer defect is located. The exposure of the photosensitive material corresponding to the area where the mask layer defect is located can be performed by using super-resolution imaging photolithography, electron beam direct writing photolithography, laser direct writing photolithography or projection photolithography.

[0040] In some embodiments, the photosensitive layer is developed by immersing the mask including the exposed photosensitive layer in a developing solution or spraying the developing solution on the photosensitive layer of the mask. The developing solution only develops the photosensitive pattern without damaging the mask layer.

[0041] For example, the developing solution can be a developing solution specially used for AR series, AZ series or other series of photoresist.

[0042] In some embodiments, the method for depositing a masking material on the front surface of the mask blank comprises: depositing the masking material on the front surface of the mask blank by evaporation deposition, magnetron sputtering deposition, atomic layer deposition or chemical vapor deposition.

[0043] The thickness of the masking material is the same as the thickness of the masking layer. The thickness of the masking material deposited on the front surface of the mask blank can be 10 nm to 500 nm.

[0044] The masking material is the same as the material of the masking layer. For example, the masking material can also be Cr, Mo or other hard metals.

[0045] In some embodiments, the method for removing the photosensitive layer can comprise: removing the photosensitive layer by dry etching or wet etching, wherein the dry etching comprises one of reactive ion etching and inductively coupled plasma etching, and the wet etching comprises etching by at least one of a stripping liquid, acetone and ethanol. The photosensitive material is removed without damaging the mask metal layer.

[0046] In some embodiments, the cleaning can comprise: cleaning the mask blank after the photosensitive layer is removed by dry cleaning or wet cleaning. The dry cleaning comprises at least one of ultraviolet ozone, supercritical CO2 cleaning and oxygen plasma etching. The wet cleaning comprises cleaning by at least one of acetone, ethanol, a mixture of sulfuric acid and hydrogen peroxide (SPM) and an alkaline cleaning agent (SCl). The cleaning can effectively remove particles or organic residues on the surface of the mask without damaging the masking layer of the mask.

[0047] It should be noted that the mask is prone to damage due to the proximity contact feature of super-resolution lithography, and therefore, the method for repairing the surface defects of the mask blank provided in the embodiments of the present disclosure can be well applied to repairing the surface defects of the super-resolution lithography mask blank.

[0048] In order to more clearly illustrate the method for repairing the surface defects of the mask blank provided in the embodiments of the present disclosure, the following will be described in detail with reference to the accompanying drawings. Figure 2 Some specific embodiments are provided, which are described by taking the repair of non-graphic area defects as an example. Among them, Figure 2 The cross-sectional structure diagrams corresponding to each stage in the repair process of the surface defects of the mask blank according to the embodiments of the present disclosure are schematically shown.

[0049] Embodiment 1

[0050] As shown in the drawings, Figure 2 The method for repairing the surface defects of the mask blank in the present embodiment 1 can comprise the following steps.

[0051] Step (1): A layer of electron beam resist is coated on the surface of the quartz substrate 1 and the Cr film layer 3 as the masking layer 3 by the spin coating method to form a photosensitive layer 4, and the thickness of the Cr film layer is 40 nm.

[0052] Step (2): Determine the non-graphic area on the masking layer 3 according to the layout of the mask. Use light to illuminate the non-graphic area on the masking layer 3 from the back of the mask, so that the light passes through the area where the defect 2 is located in the masking layer 3, and expose the photosensitive material in the area where the defect 2 is located.

[0053] Step (3): Develop the photosensitive layer 4 to remove the photosensitive material in the area where the defect 2 of the masking layer 3 of the mask is located.

[0054] Step (4): Deposit Cr masking material on the patterned structure of substrate 1 using magnetron sputtering. The thickness of the deposited Cr is 40 nm.

[0055] Step (5): Remove the photosensitive layer 4 on the front side of the mask using N-methyl-2-pyrrolidone (NMP).

[0056] Step (6): Clean the mask by irradiating it with ultraviolet ozone for 30 minutes, then cleaning it with SPM at 80°C for 15 minutes, and then drying it with the low surface tension properties of combined isopropanol (IPA) and hot nitrogen (N2). The mask is then inspected under a microscope to ensure that the defects are repaired and the repaired mask is obtained.

[0057] Example 2

[0058] like Figure 2 As shown, the method for repairing surface defects of the mask in this embodiment 2 may include the following steps.

[0059] Step (1): Using a spraying method, a layer of ultraviolet photoresist is coated on the surface of sapphire as substrate 1 and Mo film as masking layer 3 to form photosensitive layer 4. The thickness of Mo film is 120nm.

[0060] Step (2): Determine the non-graphic area on the masking layer 3 according to the layout of the mask. Use light to illuminate the non-graphic area on the masking layer 3 from the back of the mask, so that the light passes through the area where the defect 2 is located in the masking layer 3, and expose the photosensitive material in the area where the defect 2 is located.

[0061] Step (3): Develop the photosensitive layer 4 to remove the photosensitive material in the area where the defect 2 of the masking layer 3 of the mask is located.

[0062] Step (4): Atomic layer deposition is used to deposit the masking material Mo on the patterned structure of substrate 1. The thickness of the deposited Mo is 120 nm.

[0063] Step (5): Use acetone to remove the photosensitive layer 4 on the front side of the mask.

[0064] Step (6): cleaning the mask, using ultraviolet ozone irradiation for 30 minutes, then using SPM to clean at 90°C for 10 minutes, and then using SC1 to clean at 60°C for 5 minutes. The mask is checked by a microscope to be free of defects, and a repaired mask is obtained.

[0065] Example 3

[0066] As shown in FIG. 2, the method for repairing surface defects of the mask of Example 2 can include the following steps. Figure 2

[0067] Step (1): using a spraying method to coat a layer of PMMA photoresist on the surface of the glass substrate 1 and the Cr film layer 3 as a mask layer 3, forming a photosensitive layer 4, and the thickness of the Cr film layer is 200 nm.

[0068] Step (2): determining the non-patterned area on the mask layer 3 according to the layout of the mask, and using light to irradiate the non-patterned area on the mask layer 3 from the back of the mask, so that the light passes through the area where the defect 2 is located on the mask layer 3, and the photosensitive material in the area where the defect 2 is located is exposed.

[0069] Step (3): developing the photosensitive layer 4 to remove the photosensitive material in the area where the defect 2 of the mask layer 3 is located.

[0070] Step (4): using a magnetron sputtering method to deposit a mask material Cr on the pattern structure of the substrate 1, and the thickness of the deposited Cr is 200 nm.

[0071] Step (5): using acetone to remove the photosensitive layer 4 on the front of the mask.

[0072] Step (6): cleaning the mask, using ultraviolet ozone irradiation for 20 minutes, then using SPM to clean at 80°C for 10 minutes, and then using a combination of isopropyl alcohol (IPA) low surface tension characteristics and hot nitrogen gas (N2) drying, and the mask is checked by a microscope to be free of defects, and a repaired mask is obtained.

[0073] The above describes the embodiments of the present disclosure. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.​

Claims

1. A method for repairing defects in the masking layer on the surface of a photomask, characterized in that, include: A photosensitive material is coated on the front side of the photomask to form a photosensitive layer; The mask is illuminated from the back, allowing light to pass through the area where the masking layer defect is located, thus exposing the photosensitive material in the area where the masking layer defect is located. The photosensitive layer is developed to remove the photosensitive material in the area where the masking layer of the mask is defective; A masking material is deposited on the front side of the mask, the masking material filling the area where the masking layer of the mask is defective; After removing the photosensitive layer, the mask is cleaned to obtain a mask with repaired masking layer defects.

2. The repair method according to claim 1, characterized in that, The mask includes a substrate and a masking layer formed on the surface of the substrate; the substrate includes one of a quartz substrate, a glass substrate, a sapphire substrate, and an organic thin film substrate.

3. The repair method according to claim 1, characterized in that, The process of coating a photosensitive material onto the front side of a photomask to form a photosensitive layer includes: The photosensitive layer is formed by coating one of ultraviolet photoresist, electron beam photoresist, or PMMA series photoresist on the front side of the photomask.

4. The repair method according to claim 1 or 3, characterized in that, A photosensitive layer with a thickness of 30nm~500nm is formed on the front side of the photomask.

5. The repair method according to claim 1, characterized in that, The step of illuminating the mask from its back side, allowing light to pass through the area where the masking layer defect is located, and exposing the photosensitive material corresponding to the area where the masking layer defect is located, includes: The photosensitive material corresponding to the area where the masking layer defect is located is exposed using a lithography method such as super-resolution imaging lithography, electron beam direct writing lithography, laser direct writing lithography, or projection lithography.

6. The repair method according to claim 1, characterized in that, The development of the photosensitive layer includes: The photomask, including the exposed photosensitive layer, is immersed in the developing solution for development, or the developing solution is sprayed onto the photosensitive layer of the photomask for development; wherein the developing solution does not damage the masking layer of the photomask.

7. The repair method according to claim 2, characterized in that, The deposition of masking material on the front side of the mask includes: A masking material is deposited on the front side of the mask using evaporation deposition, magnetron sputtering deposition, atomic layer deposition, or chemical vapor deposition, wherein the thickness of the film formed by the masking material is the same as the thickness of the masking layer, and the masking material is the same material as the masking layer.

8. The repair method according to claim 7, characterized in that, A masking material with a thickness of 10 nm to 500 nm is deposited on the front side of the mask.

9. The repair method according to claim 1, characterized in that, The removal of the photosensitive layer includes: The photosensitive layer is removed by dry etching or wet etching, wherein the dry etching includes one of reactive ion etching and inductively coupled plasma etching, and the wet etching includes etching using at least one of resist remover, acetone, and ethanol.

10. The method according to claim 1, characterized in that, The cleaning includes: The photomask after the photosensitive layer has been removed is cleaned using either dry or wet cleaning methods; The dry cleaning method includes at least one of ultraviolet ozone, supercritical CO2 cleaning, and oxygen plasma etching. The wet cleaning method includes cleaning using at least one of acetone, ethanol, a mixture of sulfuric acid and hydrogen peroxide, or an alkaline cleaning agent.

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