A photolithography mask, a method for preparing the same and application thereof in extreme ultraviolet lithography

Abstract

The application belongs to the field of photoetching technology, and particularly relates to a photoetching mask, a preparation method thereof and application of the photoetching mask in extreme ultraviolet photoetching. The application provides a photoetching mask, which comprises a substrate layer, a silicon nitride layer and a reflection layer which are sequentially arranged in layers. The photoetching mask provided by the application uses silicon nitride as a bottom layer of the reflection layer, can well play a role of connecting the substrate layer and the reflection layer, and ensures that each film layer of the mask will not easily fall off. Meanwhile, the silicon nitride has high hardness, high temperature resistance, corrosion resistance, excellent insulation and heat conductivity and other performances, and can well maintain the stability of the extreme ultraviolet mask plate.

Description

Technical Field

[0001] This invention belongs to the field of photolithography technology, specifically relating to a photolithographic mask, its preparation method, and its application in extreme ultraviolet lithography. Background Technology

[0002] In the development of nanofabrication technology, photolithography has always been a core driving force, determining the feature size of integrated circuit components. The development of photolithography technology has progressed from equidistant photolithography to miniaturized projection photolithography, and the wavelengths used are gradually becoming shorter. Photolithographic resolution has become an important indicator affecting the development of photolithography technology. Among them, extreme ultraviolet projection photolithography has received widespread attention due to its high resolution and high production efficiency, and is considered an important milestone in photolithography technology with wavelengths of 7nm or even shorter.

[0003] Many factors influence the commercialization of extreme ultraviolet (EUV) lithography, with the photomask being one of the key factors. Since the refractive index of all materials in the EUV (11–14 nm) band is close to 1 and exhibits strong absorption, a reflective optical system is required, which places higher demands on the photomask structure. Current EUV lithography photomasks suffer from structural instability and easy detachment of the reflective layer during use. Summary of the Invention

[0004] The purpose of this invention is to provide a photolithography mask, its preparation method, and its application in extreme ultraviolet lithography. The photolithography mask provided by this invention has a stable structure and can avoid the problem of reflective layer shedding in extreme ultraviolet lithography.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a photomask comprising a substrate layer, a silicon nitride layer and a reflective layer stacked sequentially.

[0007] Preferably, the substrate layer is made of a low thermal expansion material; the coefficient of thermal expansion of the low thermal expansion material is 0 to 9 × 10⁻⁶. -6 ppm / ℃; the thickness of the substrate layer is 0.125 to 0.5 inches.

[0008] Preferably, the low thermal expansion material is quartz, glass, or elemental silicon.

[0009] Preferably, the silicon nitride in the silicon nitride layer has the chemical formula SiN. x Where x is 0.5 to 2; the silicon nitride is amorphous; and the thickness of the silicon nitride layer is 5 to 20 nm.

[0010] Preferably, the material of the reflective layer includes two or more of Mo, Si, Cr, C, B4C and Zc; the thickness of the reflective layer is 200-500 nm.

[0011] The present invention also provides a method for preparing the photomask described in the above technical solution, comprising the following steps:

[0012] Silicon nitride is deposited on one side of the substrate to obtain a silicon nitride layer;

[0013] A reflective layer is prepared on the surface of the silicon nitride layer to obtain the photomask.

[0014] Preferably, the deposited silicon nitride is deposited by physical vapor deposition.

[0015] Preferably, the physical vapor deposition is magnetron sputtering; the target material used in the magnetron sputtering is a silicon target; the power of the magnetron sputtering is 1000-3000W, and the time is 0.5-2h; the magnetron sputtering is carried out in a nitrogen-inert gas environment; the nitrogen volume concentration in the nitrogen-inert gas environment is 5-50%.

[0016] Preferably, the reflective layer is prepared by physical vapor deposition; the physical vapor deposition is magnetron sputtering.

[0017] The present invention also provides the application of the photomask described in the above technical solution or the photomask obtained by the preparation method described in the above technical solution in extreme ultraviolet lithography.

[0018] This invention provides a photolithography mask comprising a substrate layer, a silicon nitride layer, and a reflective layer stacked sequentially. The photolithography mask provided by this invention uses silicon nitride as the base layer for the reflective layer. Its unique surface morphology allows for close integration with the substrate layer or reflective layer, effectively connecting the substrate layer and the reflective layer and ensuring that the various layers of the mask do not easily detach. Simultaneously, silicon nitride possesses high hardness, high temperature resistance, corrosion resistance, and excellent insulation and thermal conductivity, which effectively maintains the stability of the extreme ultraviolet (EUV) mask. Therefore, the photolithography mask provided by this invention has a significant promoting effect on the EUV lithography industry. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The XRR test images of the photolithography mask substrate layer and silicon nitride layer obtained in Example 1 are shown.

[0021] Figure 2 The XRR test images of the photolithography mask substrate layer and silicon nitride layer obtained in Example 2 are shown.

[0022] Figure 3 The XRR test image of the photolithography mask obtained in Example 3;

[0023] Figure 4 The image shows the XRD pattern of the silicon nitride layer obtained in Example 1.

[0024] Figure 5 The image shows the XRD pattern of the silicon nitride layer obtained in Example 2.

[0025] Figure 6 This is a photograph of the substrate obtained in Example 2 after being placed for one month following the film adhesion test.

[0026] Figure 7 This is a photograph of the coated sheet obtained in Example 3 after being placed for one month following the film adhesion test.

[0027] Figure 8 This is a photograph of the film adhesion test performed on the substrate obtained in Comparative Example 1. Detailed Implementation

[0028] The present invention provides a photomask comprising a substrate layer, a silicon nitride layer and a reflective layer stacked sequentially.

[0029] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0030] In this invention, the substrate layer is preferably made of a low thermal expansion material; the coefficient of thermal expansion of the low thermal expansion material is preferably 0 to 9 × 10⁻⁶. -6 ppm / ℃, more preferably 0~5×10 -6 ppm / ℃; the low thermal expansion material is preferably quartz, glass or elemental silicon, more preferably quartz; the quartz is preferably fused silica; the glass is preferably ULE glass or borosilicate glass, more preferably ULE glass; the thickness of the substrate layer is preferably 0.125 to 0.5 inches, more preferably 0.25 to 0.4 inches, and most preferably 0.25 inches.

[0031] In this invention, the preferred chemical formula of the silicon nitride in the silicon nitride layer is SiN. x Wherein, x is preferably 0.5 to 2, more preferably 0.8 to 1.5; the silicon nitride is amorphous; the thickness of the silicon nitride layer is preferably 5 to 20 nm, more preferably 6 to 10 nm.

[0032] In this invention, the material of the reflective layer preferably includes two or more of Mo, Si, Cr, C, B4C, and Zc, more preferably two or more of Mo, Si, Cr, and C, and most preferably Mo and Si; in this invention, the reflective layer is a molybdenum / silicon multilayer film; the molybdenum / silicon multilayer film is preferably a molybdenum layer and a silicon layer stacked sequentially; the thickness of the molybdenum layer is preferably 1-5 nm, more preferably 2-4 nm; the thickness of the silicon layer is preferably 1.5-7.5 nm, more preferably 3-6 nm; the number of molybdenum and silicon layers is independently 20-100 layers, more preferably 40-80 layers; the thickness of the reflective layer is preferably 200-500 nm, more preferably 300-450 nm; in this invention, both the thickness and the number of layers are related to the incident angle, and 50 layers are optimal at 5° incident angle.

[0033] The photolithography mask provided by this invention uses silicon nitride as the base layer for the reflective layer, which effectively connects the substrate layer and the reflective layer, ensuring that the various layers of the mask do not easily detach. Simultaneously, silicon nitride possesses high hardness, high temperature resistance, corrosion resistance, and excellent insulation and thermal conductivity, which effectively maintains the stability of the extreme ultraviolet mask.

[0034] The present invention also provides a method for preparing the photomask described in the above technical solution, comprising the following steps:

[0035] Silicon nitride is deposited on one side of the substrate to obtain a silicon nitride layer;

[0036] A reflective layer is prepared on the surface of the silicon nitride layer to obtain the photomask.

[0037] The present invention deposits silicon nitride on one side of a substrate to obtain a silicon nitride layer.

[0038] In this invention, the silicon nitride deposition is preferably physical vapor deposition; the physical vapor deposition is preferably magnetron sputtering; the target material used for magnetron sputtering is preferably a silicon target; the purity of the silicon target is preferably 99.99% or higher, more preferably 99.999%; the power of the magnetron sputtering is preferably 1000-3000W, more preferably 1000-2000W; the time is preferably 0.5-2h, more preferably 0.8-1.5h; the magnetron sputtering is preferably performed in a nitrogen-inert gas environment; the nitrogen- The inert gas in the inert gas environment is preferably argon; the purity of the nitrogen is preferably 99.99% or higher, more preferably 99.999%; the purity of the argon is preferably 99.99% or higher, more preferably 99.999%; the nitrogen volume concentration in the nitrogen-inert gas environment is preferably 5-50%, more preferably 10-30%; the step of providing the nitrogen-inert gas environment is preferably: first, evacuating the magnetron sputtering equipment, and then introducing nitrogen and inert gas; the vacuum degree of the evacuation is preferably ≤3×10 -4 Pa, more preferably ≤1×10 -4 The nitrogen gas flow rate is preferably 5–50 sccm, more preferably 10–30 sccm; the inert gas flow rate is preferably 40–150 sccm, more preferably 60–120 sccm; the nitrogen and inert gas pressures are preferably 0.08–0.5 Pa, more preferably 0.1–0.3 Pa. In this invention, magnetron sputtering is used, which, compared to other methods, sputtered particles with higher energy, resulting in a denser film on the substrate—that is, higher density, better adhesion, greater hardness, and better quality. Furthermore, reactive sputtering is incorporated, using a silicon target and nitrogen gas to react and prepare silicon nitride, instead of directly using a silicon nitride target. This method allows for modification of the atomic ratio of the film, achieving an ideal ratio.

[0039] After obtaining the silicon nitride layer, the present invention prepares a reflective layer on the surface of the silicon nitride layer to obtain the photomask.

[0040] In this invention, the reflective layer is prepared by physical vapor deposition (PVD); the PVD is magnetron sputtering; the target material used for magnetron sputtering is preferably a molybdenum target or a silicon target; the purity of the molybdenum target is preferably 99.9% or higher, more preferably 99.99%; the purity of the silicon target is preferably 99.99% or higher, more preferably 99.999%; when the target material used for magnetron sputtering is a molybdenum target, the power of the magnetron sputtering is preferably 750–3000 W, more preferably 1000–2000 W; the magnetron sputtering is preferably performed in an inert gas environment; the inert gas in the inert gas environment is preferably argon; the step of providing the inert gas environment is preferably: first evacuating the magnetron sputtering equipment, and then introducing the inert gas; the vacuum degree of the evacuation is preferably ≤3×10⁻⁶. -4 Pa, more preferably ≤1×10 -4 Pa; the pressure of the inert gas is preferably 0.08-0.5 Pa, more preferably 0.1-0.3 Pa; when the target material used for magnetron sputtering is a silicon target, the power of the magnetron sputtering is preferably 1000-3000 W, more preferably 1000-2000 W; the magnetron sputtering is preferably performed in an inert gas environment; the inert gas in the inert gas environment is preferably argon; the step of providing the inert gas environment is preferably: first evacuating the magnetron sputtering equipment, and then introducing the inert gas; the vacuum degree of the evacuation is preferably ≤3×10 -4 Pa, more preferably ≤1×10 -4 Pa; the pressure of the inert gas is preferably 0.08 to 0.5 Pa, more preferably 0.1 to 0.3 Pa.

[0041] The present invention also provides the application of the photomask described in the above technical solution or the photomask obtained by the preparation method described in the above technical solution in extreme ultraviolet lithography.

[0042] In this invention, the wavelength range of the extreme ultraviolet lithography is preferably 10–121 nm, more preferably 11–14 nm, and most preferably 13.5 nm. This invention does not impose any special limitations on the application process of the photomask in extreme ultraviolet lithography; methods well-known to those skilled in the art can be used.

[0043] To further illustrate the present invention, the photolithographic mask provided by the present invention, its preparation method, and its application in extreme ultraviolet lithography are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] A 6.35mm thick smooth fused silica substrate was selected, and a smooth silicon wafer was used as the substrate. After being fixed in a fixture, the wafer was placed in a magnetron sputtering apparatus. The apparatus was evacuated until the internal pressure was less than 1.5 × 10⁻⁶ mm. -4 At a pressure of 0.12 Pa, the vacuum was stopped, and argon (Ar) gas (99.999% purity) was introduced at a flow rate of 70 sccm. The silicon (Si) target was started with a power of 1500 W, and nitrogen (N2) gas (99.999% purity) gas (28 sccm) gas (working gas pressure 0.12 Pa) was introduced to allow the N2 to fully react with the Si, forming the desired SiN particles, which were then sputtered onto the prepared substrate. A 20 nm thick silicon nitride layer with the SiN structure was obtained by uniform growth on the substrate. After growth, argon gas was introduced as a protective gas until the pressure reached 10 Pa. Then, the vent valve was slowly opened to allow atmospheric pressure to be introduced, resulting in the extreme ultraviolet lithography mask substrate layer and the silicon nitride layer.

[0046] Example 2

[0047] A 6.35mm thick smooth fused silica substrate was selected, and a smooth silicon wafer was used as the substrate. After being fixed in a fixture, the wafer was placed in a magnetron sputtering apparatus. The apparatus was evacuated until the internal pressure was less than 1.5 × 10⁻⁶ mm. -4 At a pressure of 0.11 Pa, stop evacuation and introduce argon (Ar) gas at a flow rate of 70 sccm. Start the silicon (Si) target with a power of 1500 W and introduce nitrogen (N2) gas at a flow rate of 14 sccm. The working gas pressure is 0.11 Pa. Allow N2 to react fully with Si to form the desired SiN. 0.6 The particles were sputtered onto the prepared substrate and uniformly grown to obtain a 60 nm thick silicon nitride layer with the structure SiN. After growth, argon gas was introduced as a protective gas until the pressure reached 10 Pa. Then, the vent valve was slowly opened to allow atmospheric air to be introduced, resulting in an extreme ultraviolet lithography mask substrate layer and a silicon nitride layer.

[0048] Example 3

[0049] A 6.35mm thick smooth fused silica substrate was selected, and a smooth silicon wafer was used as the substrate. After being fixed in a fixture, the wafer was placed in a magnetron sputtering apparatus. The apparatus was evacuated until the internal pressure was less than 1.5 × 10⁻⁶ mm. -4 At a pressure of 0.115 Pa, the vacuum was stopped, and argon (Ar) gas was introduced at a flow rate of 70 sccm. The silicon (Si) target was started with a power of 1500 W, and nitrogen (N2) gas was introduced at a flow rate of 21 sccm. The working gas pressure was 0.115 Pa. The N2 was allowed to react fully with Si to form the desired SiN particles, which were then sputtered onto the prepared substrate. A uniform growth was then achieved to obtain an 8 nm thick silicon nitride layer with the structure SiN. 0.75After growth, a 2.75 nm thick molybdenum (Mo) layer was prepared by magnetron sputtering, with the following parameters: Mo target (99.99% purity), and base vacuum ≤ 1 × 10⁻⁶. -4 The system operates at 1000W power and uses argon gas at a pressure of 0.1Pa. A 4.2nm thick Si layer is fabricated on a Mo layer using magnetron sputtering. Parameters include: Si target (99.999% purity), and a base vacuum ≤1×10⁻⁶. -4 The power was 1500W, the working gas was argon, and the working gas pressure was 0.1Pa. Then, Mo / Si of the same thickness was deposited repeatedly for a total of 50 cycles. After the growth was completed, argon protective gas was introduced until the pressure reached 10Pa. Then, the vent valve was slowly opened to introduce atmospheric air, resulting in an extreme ultraviolet lithography mask.

[0050] Comparative Example 1

[0051] An extreme ultraviolet lithography mask was prepared according to the technical solution provided in Example 3, the only difference being that no silicon nitride layer was deposited.

[0052] Test Example 1

[0053] XRR tests were performed on the substrate layer and silicon nitride layer or photomask obtained in Examples 1-3. The XRR spectra corresponding to Examples 1-3 are shown below. Figures 1-3 XRD tests were performed on the photolithographic mask substrate layer and silicon nitride layer obtained in Examples 1 and 2. The XRD patterns corresponding to Examples 1 and 2 are shown below. Figures 4-5 .

[0054] Depend on Figures 1-2 It can be seen that the SiN thin films deposited in Examples 1 and 2 have stable structures and good film quality.

[0055] Depend on Figure 3 It can be seen that the Mo / Si reflective layer deposited on silicon nitride still has a relatively obvious diffraction peak at 12°, indicating a relatively high film thickness, which does not affect its reflection efficiency.

[0056] Depend on Figures 4-5 As can be seen, the XRD image shows no obvious diffraction peaks, indicating that there is no crystallization. The silicon nitride layer obtained in this invention has an amorphous structure and is colorless and transparent.

[0057] Test Example 2

[0058] The film adhesion of the substrates obtained in Examples 1-3 and Comparative Example 1 was tested using a tape tear test. The film condition of the substrates obtained in Examples 1-3 after being placed under atmospheric conditions for one month was observed. A photograph of the substrate obtained in Example 2 after one month of placement following the film adhesion test is shown below. Figure 6The physical image of the coated sheet obtained in Example 3 after being placed for one month following the film adhesion test is shown below. Figure 7 The actual image of the film adhesion test performed on the surcharged sheet obtained in Example 1 is shown below. Figure 8 .

[0059] The experimental results show that the substrate films obtained in Examples 1-3 did not detach after the film was peeled off. Furthermore, after being placed in atmospheric conditions for one month, the film layers remained intact, colorless, and transparent, without any oxidation or other deterioration issues, and their performance remained essentially unchanged. In contrast, the substrate film obtained in Comparative Example 1 detached after the film was peeled off, indicating poor adhesion of the mask used to directly prepare the reflective layer on the substrate.

[0060] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A photolithographic mask, characterized in that, It consists of a substrate layer, a silicon nitride layer, and a reflective layer stacked sequentially. The material of the reflective layer includes two or more of Mo, Si, Cr, C and B4C; The thickness of the silicon nitride layer is 5–20 nm; The method for preparing the photomask includes the following steps: Silicon nitride is deposited on one side of the substrate to obtain a silicon nitride layer; A reflective layer is prepared on the surface of the silicon nitride layer to obtain the photomask.

2. The photolithographic mask according to claim 1, characterized in that, The base layer is made of a low thermal expansion material; The coefficient of thermal expansion of the low thermal expansion material is 0 to 9 × 10⁻⁶. -6 ppm / ℃; the thickness of the substrate layer is 0.125 to 0.5 inches.

3. The photolithographic mask according to claim 2, characterized in that, The low thermal expansion material is quartz, glass, or elemental silicon.

4. The photolithographic mask according to claim 1, characterized in that, The silicon nitride in the silicon nitride layer has the chemical formula SiN. x Where x is 0.5 to 2; the silicon nitride is amorphous.

5. The photolithographic mask according to claim 1, characterized in that, The thickness of the reflective layer is 200–500 nm.

6. The method for preparing the photomask according to any one of claims 1 to 5, characterized in that, Includes the following steps: Silicon nitride is deposited on one side of the substrate to obtain a silicon nitride layer; A reflective layer is prepared on the surface of the silicon nitride layer to obtain the photomask.

7. The preparation method according to claim 6, characterized in that, The deposited silicon nitride is a physical vapor deposition.

8. The preparation method according to claim 7, characterized in that, The physical vapor deposition is magnetron sputtering; the target material used in the magnetron sputtering is a silicon target; the power of the magnetron sputtering is 1000-3000W, and the time is 0.5-2h; the magnetron sputtering is carried out in a nitrogen-inert gas environment; the nitrogen volume concentration in the nitrogen-inert gas environment is 5-50%.

9. The preparation method according to claim 6, characterized in that, The reflective layer is prepared by physical vapor deposition; the physical vapor deposition is magnetron sputtering.

10. The application of the photomask according to any one of claims 1 to 5 or the photomask obtained by the preparation method according to any one of claims 6 to 9 in extreme ultraviolet lithography.

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