Reflective EUV mask plate and manufacturing method thereof

Abstract

A reflective EUV mask plate and a manufacturing method thereof, the reflective EUV mask plate comprising: a transparent substrate, a reflective film disposed on one side surface of the transparent substrate, the reflective film having a plurality of molybdenum-silicon alternating layers, a protective layer disposed on the reflective film, and a patterned absorbing layer disposed on the protective layer, the patterned absorbing layer is provided with an inclined side wall, and the width of the patterned absorbing layer is gradually narrowed from the upper surface of the patterned absorbing layer to the surface of the reflecting film. The reflective EUV mask plate can optimize the light path efficiency, improve the reflection intensity and effectively improve the imaging resolution, and has the beneficial effects of high reflection intensity and high imaging resolution. Correspondingly, the invention also provides a manufacturing method of the reflective EUV mask plate.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing technology, and in particular to an EUV mask and its manufacturing method. Background Technology

[0002] Extreme ultraviolet (EUV) lithography is a key process in semiconductor manufacturing, and its resolution directly affects the reduction of feature sizes in integrated circuits. In reflective EUV masks, patterns are formed by absorber layers. The absorber layers define dark areas by blocking part of the EUV light, while bright areas composed of multiple Bragg mirrors are responsible for reflecting EUV light. To achieve high-resolution pattern transfer, the absorber patterns on the mask typically require highly precise dimensional control while maintaining high reflective contrast.

[0003] Generally, EUV light is incident on the mask surface at an angle of approximately 6 degrees, and correspondingly, the reflected light returns obliquely upward at an angle of 6 degrees. In traditional reflective EUV masks, the absorber typically employs a vertical sidewall profile. The optical path of the obliquely reflected light at the edge of the bright area is physically blocked by the absorber's sidewall, causing some of the light that should have been reflected to be absorbed or scattered and lost. This reduces the effective reflection intensity of the bright area and affects the reflective performance of the EUV mask. This effect is particularly pronounced when the pattern size is further reduced, becoming a key factor limiting the resolution of EUV masks.

[0004] Therefore, existing EUV masks suffer from technical problems such as low reflection intensity and limited resolution. Summary of the Invention

[0005] The purpose of this invention is to provide a reflective EUV mask and its manufacturing method to solve the technical problems of low reflectivity and limited resolution of EUV masks in the prior art.

[0006] To achieve the above objectives, in one aspect, the present invention provides a reflective EUV mask, comprising: a transparent substrate, a reflective film, a protective layer, and a patterned absorption layer. A reflective film is disposed on one side surface of the transparent substrate. The reflective film has multiple alternating molybdenum-silicon layers. A protective layer is disposed on the reflective film. A patterned absorption layer is disposed on the protective layer. The patterned absorption layer has inclined sidewalls, and the width of the patterned absorption layer gradually narrows from the upper surface of the patterned absorption layer to the surface of the reflective film.

[0007] In the aforementioned reflective EUV mask, the patterned absorption layer has inclined sidewalls, and the width of the patterned absorption layer gradually narrows from the upper surface of the absorption layer to the surface of the protective layer. The sidewalls of the patterned absorption layer gradually contract inward from the upper surface of the absorption layer to the surface of the protective layer. For incident light incident obliquely into the bright area, the inclination direction of the sidewall of the absorption layer on one side of the bright area is opposite to the incident direction of the light, and it will not affect the transmission of the incident and reflected light. The inclination direction of the sidewall of the absorption layer on the other side of the bright area is the same as the incident direction of the light. The sidewall of the absorption layer is approximately parallel or parallel to the incident light, which can greatly reduce the influence of the sidewall of the absorption layer on the transmission of the incident and reflected light, so that the amount of light received and reflected in the bright area is greater, which can significantly improve the output of reflected light, effectively enhance the reflection intensity of the bright area, and improve the resolution.

[0008] Therefore, the aforementioned reflective EUV mask can optimize optical path efficiency, improve reflection intensity, and effectively improve imaging resolution, thus having the beneficial effects of high reflection intensity and high imaging resolution.

[0009] In one embodiment, the tilt angle of the inclined sidewall is not less than 6°.

[0010] In one embodiment, the tilt angle of the inclined sidewall is no greater than 10°.

[0011] On the other hand, the present invention also provides a method for manufacturing a reflective EUV mask, comprising the following steps: Provide transparent substrates; A molybdenum-silicon alternating layer is deposited on one side surface of a transparent substrate to form a reflective film; Deposit a protective layer on the reflective film; Deposit an absorption layer on the protective layer; A negative bias voltage is applied to the transparent substrate, and the absorption layer is patterned by focused ion beam etching to form a patterned absorption layer. The focused ion beam contains reactive ions and sputtered ions.

[0012] In one embodiment, the reacting ions include chloride ions or fluoride ions.

[0013] In one embodiment, the sputtered ions are argon ions.

[0014] In one embodiment, The step of patterning the absorption layer by focused ion beam etching also includes the following steps: The absorption layer is graphically scanned to form alignment marks; or, After the step of patterning the absorption layer by focused ion beam etching, the following steps are also included: A back conductive layer is deposited on the other side surface of the transparent substrate.

[0015] In one embodiment, the negative bias voltage applied to the transparent substrate is 100V~500V.

[0016] In one embodiment, the focused ion beam flux is no greater than 1 mA / µm. 2 The energy of the focused ion beam is no greater than 100 eV; or, The chamber pressure of the etching chamber is no greater than 10 mTorr.

[0017] In one embodiment, the beam spot size of the focused ion beam is no greater than 5 nm.

[0018] The aforementioned method for manufacturing a reflective EUV mask involves applying a negative bias voltage to a transparent substrate and using a focused ion beam containing sputtered ions and reactive ions to perform patterned etching scanning on the absorption layer. After scanning, a patterned absorption layer with tilted sidewalls is formed. This method is used to manufacture any of the reflective EUV masks described above, optimizing the optical path efficiency and improving the reflection intensity of the reflective EUV mask. This effectively improves the imaging resolution of the reflective EUV mask, offering the beneficial effects of enhancing both the reflection intensity and imaging resolution. Furthermore, the aforementioned method uses a focused ion beam to perform patterned etching scanning on the absorption layer, directly forming a patterned absorption layer after scanning. This eliminates the need for patterning processes such as coating, exposure, and etching in traditional EUV mask manufacturing processes, simplifying the EUV mask fabrication process, effectively improving EUV mask production efficiency, and saving manufacturing costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a reflective EUV mask according to one embodiment; Figure 2 A schematic diagram of light transmission in a pair of proportional reflective EUV masks; Figure 3 This is a schematic diagram of light transmission for another pair of proportional reflective EUV masks; Figure 4 A schematic diagram of light transmission in a reflective EUV mask according to an embodiment; Figure 5 This is a flowchart illustrating a method for manufacturing a reflective EUV mask according to one embodiment. Figure 6 This is an etching principle diagram of a focused ion beam etching scan for patterning an absorption layer, as shown in one embodiment.

[0020] Explanation of reference numerals in the attached figures: 10-Transparent substrate, 20-Reflective film, 30-Protective layer, 40-Patterned absorption layer, 41, 41'-Sloping sidewalls, 50-Bright area, 60-Reflective EUV mask. Detailed Implementation

[0021] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid confusion with the invention. It should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The same reference numerals denote the same elements throughout. It should be understood that when a layer is referred to as being formed on other layers, it may be formed directly on the other layers, or there may be intervening film layers. The terms “upper,” “lower,” “front,” “back,” etc., indicating orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention, wherein “longitudinal” can be understood as a direction perpendicular to the substrate surface, and “lateral” can be understood as a direction parallel to the substrate surface. When used herein, the singular forms "a," "an," and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "comprising" is used to identify the presence of features, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups. When used herein, the term "and / or" includes any and all combinations of the associated listed items. The terms "identical," "equal," and "consistent" include the meaning of being completely equal and identical, and may also include the meaning of being approximately identical or approximately equal within permissible process tolerances. The terms "first," "second," etc., in the specification are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological sequence. It should be understood that these terms, as used herein, may be replaced where appropriate, for example, to enable the embodiments of the invention described herein to operate in a different order than that described or shown herein. Similarly, if the methods described herein comprise a series of steps, and the order of these steps presented herein is not necessarily the only possible order in which these steps can be performed, and some of the described steps may be omitted and / or some other steps not described herein may be added to the method. If a component in one figure is the same as a component in another figure, although these components are easily identifiable in all figures, this specification will not label all identical components in every figure for the sake of clarity of description.

[0022] The present invention will be described more clearly and completely by way of embodiments and in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the following embodiments.

[0023] Please also refer to Figures 1 to 4 One embodiment of the reflective EUV mask 60 includes a transparent substrate 10, a reflective film 20, a protective layer 30, and a patterned absorption layer 40. The reflective film 20 is disposed on one side surface of the transparent substrate 10. The reflective film 20 has multiple alternating molybdenum-silicon layers. The protective layer 30 is disposed on the reflective film 20. The patterned absorption layer 40 is disposed on the protective layer 30. The patterned absorption layer 40 has inclined sidewalls 41, and the width of the patterned absorption layer 40 gradually narrows from the upper surface of the patterned absorption layer 40 to the surface of the reflective film 20.

[0024] Please refer to the following first. Figure 2 In a pair of proportional reflective EUV masks 60, the sidewalls of the absorption layer are perpendicular to the reflective film 20, and the cross-sectional profile of the bright area 50 is rectangular. Since the incident light is incident at a 6° angle, the reflected light returns obliquely upwards from the reflective film 20 at a 6° angle. A large portion of the reflected light at the edge of the bright area 50 is blocked by the sidewalls of the absorption layer, resulting in absorption or scattering loss of the reflected light. This leads to a significant loss of effective reflected light intensity, resulting in poor edge contrast and reduced resolution in the image.

[0025] Please refer to the following: Figure 3 In another example, the patterned absorption layer 40 has inclined sidewalls 41' extending outwards from the upper surface of the absorption layer to the surface of the protective layer 30. The width of the patterned absorption layer 40 gradually increases from the upper surface of the patterned absorption layer 40 to the surface of the protective layer 30, and the cross-sectional profile of the patterned absorption layer 40 is a positive cone. Correspondingly, the cross-sectional profile of the bright area 50 is a negative cone. In this example, the bottom of the absorber is wider than the top, and the sidewalls of the absorption layer on both sides of the bright area 50 extend towards the bright area 50. Not only is the reflected light path blocked by the sidewall of the absorption layer on one side, but the incident light is also blocked by the sidewall of the absorption layer on the other side. This results in a smaller total amount of light received and reflected by the reflective film 20, severely degrading its optical performance and causing poor imaging resolution.

[0026] In this embodiment, the patterned absorption layer 40 has inclined sidewalls 41, and the width of the patterned absorption layer 40 gradually narrows from its upper surface to the surface of the reflective film 20. For example... Figure 4As shown, from the upper surface of the absorption layer to the surface of the protective layer 30, the sidewalls of the absorption layer gradually taper inward to form inclined sidewalls 41. The cross-sectional profile of the patterned absorption layer 40 is a negative cone, and correspondingly, the cross-sectional profile of the bright area 50 is a positive cone. For incident light incident obliquely into the bright area 50, the inclination direction of the sidewall of the absorption layer on one side of the bright area 50 is opposite to the incident direction of the light, and it does not affect the transmission of the incident and reflected light. The inclination direction of the sidewall of the absorption layer on the other side of the bright area 50 is the same as the incident direction of the light. The sidewall of the absorption layer is approximately parallel or parallel to the incident light, which can greatly reduce the influence of the sidewall of the absorption layer on the transmission of the incident and reflected light, so that the bright area 50 receives and reflects more light, which can significantly improve the output of reflected light, effectively enhance the reflection intensity of the bright area 50, and improve the resolution. Specifically, along the propagation path of the reflected light, the sidewalls of the absorption layer contract away from the bright area 50, greatly reducing the obstruction of the reflected light. The sidewalls of the absorption layer physically obstruct the reflected light at the edge of the bright area 50, which can effectively reduce the absorption or scattering loss of the reflected light, allowing the bright area 50 to reflect more light.

[0027] In addition, the critical dimension (CD) of the reflective EUV mask 60 in this embodiment is defined by the top opening of the bright area 50. The reflected light mainly carries information about the edge of the top opening. The slight enlargement at the bottom will not be directly replicated in the image. The inverted conical design of the absorption layer keeps the top opening of the bright area 50 minimized and precisely controllable, which is further beneficial to high-resolution imaging.

[0028] In summary, the aforementioned reflective EUV mask 60 can optimize optical path efficiency, improve reflection intensity, and effectively improve imaging resolution, thus exhibiting the beneficial effects of high reflection intensity and high imaging resolution.

[0029] In one embodiment, the tilt angle of the inclined sidewall 41 is not less than 6°. Specifically, the tilt angle of the inclined sidewall 41 is the angle between the inclined sidewall 41 and the vertical direction. In this embodiment, the tilt angle of the inclined sidewall 41 is not less than 6°, which can minimize the impact of the inclined sidewall 41 on the transmission of incident and reflected light, and alleviate the obstruction of incident and reflected light by the inclined sidewall 41 to the greatest extent, so that the useful reflected light signal is strongest and the loss is minimal. Further, in one embodiment, to ensure the structural stability and reliability of the absorption layer, it is preferable that the tilt angle of the inclined sidewall 41 is not greater than 10°.

[0030] On the other hand, the present invention also provides a method for manufacturing a reflective EUV mask, which is used to manufacture the reflective EUV mask 60 described in any of the above embodiments, such as... Figure 5 As shown, the method includes the following steps: Step S11: Provide a transparent substrate 10.

[0031] Specifically, the transparent substrate 1010 includes one of a quartz substrate, a soda lime substrate, a borosilicate substrate, an aluminum silicate substrate, a silicon substrate, and a silicon carbide substrate. The radial dimension of the transparent substrate 10 is between 1 inch and 100 inches, and the thickness is between 0.1 mm and 200 mm. For example, in this embodiment, the transparent substrate 1010 can be a quartz substrate, and its radial dimension can be 4 inches, 6 inches, 8 inches, 12 inches, etc.

[0032] Step S12: Deposit a molybdenum-silicon alternating layer on one side surface of the transparent substrate 10 to form a reflective film 20.

[0033] Specifically, molybdenum layers and silicon layers (or silicon layers and molybdenum layers) are sequentially and alternately deposited on the transparent substrate 10 to form a multilayer reflective Bragg stack as a reflective film 2020. The thickness of each molybdenum layer or silicon layer is 3nm~4nm, and each pair is about 6.75nm thick. Specifically, 40-50 cycles can be deposited through deposition processes such as CVD, PECVD, PVD or ALD to form the reflective film 2020.

[0034] Step S13: Deposit a protective layer 30 on the reflective film 20.

[0035] Specifically, the protective layer 30 is preferably formed of ruthenium (Ru), and the thickness of the protective layer 30 is preferably 2nm-4nm. Further, the protective layer 30 is preferably deposited on the surface of the reflective film 2020 using deposition processes such as CVD, PECVD, PVD, and ALD.

[0036] Step S14: Deposit an absorption layer on the protective layer 30.

[0037] Specifically, the absorber layer is preferably formed using a tantalum (Ta)-based material (such as TaN), and the thickness of the absorber layer is preferably 50 nm-70 nm. Further, the absorber layer is preferably deposited on the surface of the protective layer 30 using deposition processes such as CVD, PECVD, PVD, and ALD.

[0038] Step S15: Apply a negative bias voltage to the transparent substrate 10 and perform patterned focused ion beam etching scanning on the absorption layer to form a patterned absorption layer 40.

[0039] Specifically, the focused ion beam includes reactive ions and sputtered ions. In one embodiment, the reactive ions preferably include chloride ions or fluoride ions. Further, the sputtered ions are preferably argon ions. This embodiment uses sputtered ions and reactive ions together to perform direct-write etching scanning of the absorber layer through physical sputtering and chemical etching. During the patterned etching scanning process, a negative bias voltage is applied to the substrate to form a patterned absorber layer 40 with inclined sidewalls 41. The sidewalls of the patterned absorber layer 40 gradually contract inward from the upper surface of the patterned absorber layer 40 to the surface of the reflective film 20, forming a patterned absorber layer 40 with a negative cone cross-sectional profile. Figure 6 As shown, in this embodiment, applying a negative bias voltage to the substrate creates an electric field at the edge of the absorption layer. This negative bias electric field attracts positive ions (Ar). + F + or Cl + ), thereby enhancing sidewall etching (through F + or Cl + ) and sputtering bombardment (via Ar + Furthermore, from the upper surface of the absorption layer to the surface of the reflective film 20, the negative bias voltage field intensity gradually increases, and as the etching depth increases, the sidewall etching gradually intensifies, thereby forming an inwardly contracting inclined sidewall 41 in the patterned absorption layer 40, realizing the negative cone cross-sectional profile of the patterned absorption layer 40.

[0040] Generally, during FIB (Focused Ion Beam) etching, chemical etching products may redeposit on nearby sidewalls, forming a "redeposit" layer that can cause blurred patterns and alter sidewall morphology. This embodiment incorporates high-energy Ar into the focused ion beam. + As sputtered ions, high-energy Ar + The focused ion beam can continuously bombard the sidewalls, especially the bottom region, effectively removing or thinning these redeposited deposits, ensuring the smoothness and linearity of the inclined sidewall 41, and making the tilt angle control of the inclined sidewall 41 more precise. Specifically, in this embodiment, the tilt angle of the inclined sidewall 41 can be precisely controlled by adjusting the energy and flow rate of the focused ion beam and the negative bias voltage of the substrate. In one embodiment, to ensure the etching rate and accurately control the tilt angle of the etched inclined sidewall 41, the negative bias voltage applied to the transparent substrate 10 is preferably 100V~500V. More preferably, the flow rate of the focused ion beam is not greater than 1mA / um2, and the energy of the focused ion beam is not greater than 100eV. Furthermore, in one embodiment, to further enhance the etching directionality of the focused ion beam, the chamber pressure of the etching chamber is preferably not greater than 10mTorr.

[0041] The reflective EUV mask manufacturing method of this embodiment directly forms a patterned absorption layer 40 by using a focused ion beam to perform patterned direct-write etching scanning on the absorption layer. To achieve optimal pattern control, the scanning area of ​​the focused ion beam etching needs to be adjusted according to the pattern size. To ensure that the scanning area of ​​the focused ion beam etching matches the image size and meets the patterning requirements, in one embodiment, the beam spot size of the focused ion beam is no greater than 5 nm.

[0042] In one embodiment, step S15 further includes the following step: performing a patterned scan of the absorption layer to form an alignment mark. In this embodiment, the patterned scan of the alignment mark is completed simultaneously during the patterned focused ion beam etching scan of the absorption layer, eliminating the need for separate exposure to form the alignment mark, which helps to improve the production efficiency of the reflective EUV mask 60.

[0043] Further, in one embodiment, the reflective EUV mask 60 preferably further includes a back conductive layer disposed on the other side surface of the transparent substrate 10. More preferably, after step S15, the method further includes the following step: depositing the back conductive layer on the other side surface of the transparent substrate 10 to form the reflective EUV mask 60. Specifically, after forming the patterned absorption layer 40, the back conductive layer is deposited on the other side surface of the transparent substrate 10 to complete the fabrication of the reflective EUV mask 60. Preferably, the back conductive layer is formed of materials such as Cr, Cr oxide, or Cr nitride.

[0044] The aforementioned method for manufacturing a reflective EUV mask involves applying a negative bias voltage to a transparent substrate 10 and using a focused ion beam containing sputtered ions and reactive ions to perform patterned etching scanning on the absorption layer. After scanning, a patterned absorption layer with tilted sidewalls 41 can be formed. This method is used to manufacture the reflective EUV mask 60 described above, optimizing the optical path efficiency of the reflective EUV mask 60, improving its reflection intensity, and effectively improving its imaging resolution. It has the beneficial effects of enhancing the reflection intensity and improving the imaging resolution of the reflective EUV mask 60. Furthermore, the aforementioned method uses a focused ion beam to perform patterned etching scanning on the absorption layer, directly forming the patterned absorption layer 40 after scanning. This eliminates the need for patterning processes such as coating, exposure, and etching in traditional EUV mask manufacturing processes, simplifying the EUV mask fabrication process, effectively improving EUV mask production efficiency, and saving manufacturing costs.

[0045] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the present invention.

Claims

1. A reflective EUV reticle, characterized in that Comprising: a transparent substrate, a reflective film, a protective layer and a patterned absorption layer, one side surface of the transparent substrate is provided with the reflective film, the reflective film has a plurality of layers of molybdenum-silicon alternating layers, the protective layer is arranged on the reflective film, the patterned absorption layer is arranged on the protective layer, the patterned absorption layer has an inclined side wall, and the width of the patterned absorption layer gradually narrows from the upper surface of the patterned absorption layer to the surface of the reflective film.

2. The reflective EUV reticle according to claim 1, characterized in that The inclination angle of the inclined side wall is not less than 6°.

3. The reflective EUV reticle according to claim 1, characterized in that The inclination angle of the inclined side wall is not greater than 10°.

4. A manufacturing method of a reflective EUV mask blank, characterized by, Comprising the following steps: providing a transparent substrate; depositing molybdenum-silicon alternating layers on one side surface of the transparent substrate to form a reflective film; depositing a protective layer on the reflective film; depositing an absorption layer on the protective layer; applying a negative bias to the transparent substrate and performing a patterned focused ion beam etching scan on the absorption layer to form a patterned absorption layer; The focused ion beam contains reactive ions and sputtering ions.

5. The manufacturing method of a reflective EUV mask blank according to claim 4, characterized in that, The reactive ion includes chloride ion or fluoride ion.

6. The manufacturing method of a reflective EUV reticle according to claim 4, characterized in that, The sputtering ion is argon ion.

7. The manufacturing method of the reflective EUV mask plate according to claim 5, wherein, The step of performing a patterned focused ion beam etching scan on the absorption layer to form a patterned absorption layer further comprises the following steps: performing a patterned scan on the absorption layer to form an alignment mark.

8. The manufacturing method of a reflective EUV mask blank according to claim 5, characterized in that, The negative bias applied to the transparent substrate is 100V-500V.

9. The manufacturing method of a reflective EUV mask blank according to claim 5, characterized in that, The focused ion beam has a current not greater than 1 mA / um 2 The focused ion beam has an energy not greater than 100 eV. Or, The chamber pressure of the etching chamber is not greater than 10mTorr.

10. The manufacturing method of a reflective EUV mask blank according to claim 5, characterized in that, The beam spot size of the focused ion beam is not greater than 5nm.

Images