Thin-type photomask blank based on Fobrieif interference principle and manufacturing method of thin-type photomask blank

Abstract

The invention discloses a thin-type photomask blank based on the Faraday-Bay interference principle and a manufacturing method thereof, and relates to the technical field of semiconductors, and the thin-type photomask blank comprises a transparent substrate, a surface anti-reflection layer, a Faraday-Bay cavity, a first metal reflection layer and a second metal reflection layer. According to the thin photomask, the blank structure is simple, the first metal reflecting layer and the second metal reflecting layer are used for forming a method-culture cavity, then the light shading film is thinned, and it is ensured that the contrast ratio and precision of the produced photomask meet the production standard; the manufacturing method of the thin photomask blank is simple, the technological process is simple, manufacturing of the thin photomask blank can be achieved only through the simple technology, the operation difficulty is low, the method can be widely applied to a production line, and large-scale mass production is achieved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a thinned mask blank based on the Fabry-Perot interference principle and a manufacturing method thereof. Background Art

[0002] In recent years, with the high integration of large-scale integrated circuits, the miniaturization of circuit patterns or wiring patterns, and the miniaturization of contact hole patterns used to form interlayer wiring of units, the requirements for micro-processing technology have become increasingly higher. Therefore, in the field of mask manufacturing technology, the requirements for the production of masks for chip production have also become more sophisticated, and further development of the technology for the correct circuit pattern (shielding pattern) is required.

[0003] The conventional chrome-plated binary intensity mask (BIM) on glass cannot support the required minimum feature size, linearity and through-hole spacing requirements due to the thick film layer. Generally, when forming a mask pattern, if the mask pattern is miniaturized but the thickness of the corresponding photoresist film is not reduced, the aspect ratio (ratio between the thickness of the photoresist film and the width of the pattern) of the photoresist used as the etching mask of the light-shielding film increases. In general, the mask pattern will become more prone to deterioration as the aspect ratio of the photoresist pattern increases, that is, the photoresist pattern is used as an etching mask, and its transfer accuracy to the light-shielding film will decrease. In extreme cases, part of the pattern may fall off or peel off, resulting in defects in the pattern. Therefore, when the mask pattern becomes finer, the thickness of the photoresist film used as the etching mask of the light-shielding film must be reduced to avoid an undesirable high aspect ratio. However, when the photoresist pattern is used as a mask to produce a pattern by etching the light-shielding film, a photoresist that is too thin will be etched and cannot protect the pattern position that should not be etched. One way to solve this problem is to thin the light-shielding film so that the light-shielding film patterning is completed within the time when the photoresist film thickness is still half. However, the thinning of the light-shielding film will make the light-shielding film unable to block enough exposure, resulting in poor contrast of the produced mask. Summary of the invention

[0004] The object of the present invention is to provide a thinned mask blank based on the Fabry-Perot interference principle and a manufacturing method thereof, so as to improve the above technical problems.

[0005] In order to solve the problem that when miniaturizing the mask pattern in the prior art, the thickness of the photoresist film will cause the mask pattern to be easily degraded as the aspect ratio of the photoresist pattern increases, and the accuracy of transferring the photoresist pattern to the light-shielding film will decrease, the present invention provides the following technical solutions:

[0006] A thinned photomask blank based on the Fabry-Perot interference principle comprises a substrate for producing a photomask; the substrate comprises a light shielding film and a transparent substrate; the light shielding film comprises a surface anti-reflection layer, a back anti-reflection layer, a Fabry-Perot cavity, a first metal reflection layer and a second metal reflection layer;

[0007] The back anti-reflection layer is placed on the top of the transparent substrate; the first metal reflective layer is placed on the top of the back anti-reflection layer; the Fabry-Perregaux cavity is placed on the top of the first metal reflective layer; the second metal reflective layer is placed on the top of the Fabry-Perregaux cavity; and the surface anti-reflection layer is placed on the top of the second metal reflective layer.

[0008] The Fabry-Perot cavity is obtained based on the Fabry-Perot interferometer. The inner surfaces of the two mirrors of the Fabry-Perot interferometer have high reflectivity. When the light is reflected and interfered multiple times in the Fabry-Perot cavity, only the light of a specific wavelength that meets the specific resonance conditions can be enhanced in the Fabry-Perot cavity, while the light of other wavelengths can be weakened. This can improve the monochromaticity of the light and accurately control the interference effect of the light, thereby improving the clarity and contrast of the mask pattern and realizing the miniaturization of the mask pattern.

[0009] In order to solve the problem that the photoresist film is too thick, causing part of the mask pattern to fall off or shift in position, thereby failing to obtain a complete mask pattern, further, the Fab-Pei cavity is a semi-transmissive film; the material of the semi-transmissive film is chromium, oxygen and nitrogen or molybdenum, silicon, oxygen and nitrogen, the refractive index of the semi-transmissive film is greater than 2.3, and the extinction coefficient of the semi-transmissive film is less than 1. The use of chromium, oxygen and nitrogen or molybdenum, silicon, oxygen and nitrogen to make the semi-transmissive film can reduce the thickness of the Fab-Pei cavity and reduce the process difficulty of making the Fab-Pei cavity. Since the refractive index of the semi-transmissive film is greater than 2.3 and the extinction coefficient of the semi-transmissive film is less than 1, the light absorption and scattering of the mask pattern during the exposure process can be reduced, so that most of the light is reflected or transmitted, and then the thickness of the Fab-Pei cavity can be reduced, the aspect ratio of the mask pattern is prevented from increasing, the problem of pattern falling off or position shifting is effectively reduced, the integrity, accuracy and clarity of the pattern are improved, and the loss of the thin mask blank during use is reduced.

[0010] Optical density is an influencing factor of the contrast and clarity of the mask pattern. The reduction in the thickness of the light-shielding layer will, to a certain extent, cause the light-shielding film to be unable to shield sufficient exposure, and the contrast of the produced mask will be poor. Furthermore, the structure and material of the first metal reflective layer and the second metal reflective layer are the same; the material of the first metal reflective layer is molybdenum and silicon or chromium; when the material of the first metal reflective layer is molybdenum and silicon, the content of molybdenum is greater than or equal to 60%. Since molybdenum has a high reflectivity, the reflection ability of the first metal reflective layer can be improved, and the light interference effect of the Fabry-Perez cavity can be enhanced. The combination of molybdenum and silicon can improve the light transmission characteristics, and is suitable for scenes where the refractive index of the semi-transmissive film is greater than 2.3 and the extinction coefficient is less than 1, which helps to reduce the light loss of the mask pattern during transmission and improve the transmittance of light. When the content of molybdenum is greater than or equal to 60%, the stability and durability of the first metal reflective layer can be effectively increased, and the optical density of the thinned mask blank can be achieved to exceed 2.5 or reach 3.

[0011] A method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle, comprising:

[0012] S1, cleaning the transparent substrate;

[0013] S2, placing the cleaned transparent substrate in a sputtering device for sputtering, sequentially forming a back anti-reflection layer, a first metal reflection layer, a Fabry-Perez cavity, a second metal reflection layer, and a surface anti-reflection layer, to obtain an original thinned mask blank;

[0014] S3, using a hot plate annealing device to heat treat the original thinned mask blank to obtain a thinned mask blank. This manufacturing method can realize a thinned mask blank based on the Fabry-Perot interference principle.

[0015] Furthermore, the cleaning of the transparent substrate comprises:

[0016] S1-1, irradiate the transparent substrate with ultrasound or ultraviolet rays, and perform initial cleaning on the transparent substrate with ultrapure water or functional water. Since particles on the substrate may cause unclear production mask patterns, initial cleaning of the transparent substrate can remove particles on the transparent substrate or on the surface of the thin film formed on the substrate, ensure the accuracy of the mask pattern, improve the yield rate, and maintain the long-term stability and optical performance of the thin mask blank.

[0017] S1-2. The transparent substrate is cleaned for a second time using a sulfur-free cleaning method to further ensure that the production requirements of the original thinned mask blank are met, thereby avoiding the presence of sulfides on the substrate, which in turn affects the propagation and reflection characteristics in the Fabry-Perez cavity.

[0018] Furthermore, the cleaned transparent substrate is placed in a sputtering device for sputtering to sequentially generate a back anti-reflection layer, a first metal reflection layer, a Fabry-Perez cavity, a second metal reflection layer, and a surface anti-reflection layer to obtain an original thinned mask blank, including:

[0019] S2-1, placing the cleaned transparent substrate in a sputtering device, setting a first gas pressure and a first sputtering power, inputting a first gas atmosphere into the sputtering device, and sputtering the upper surface of the cleaned transparent substrate through a chromium target to generate the back anti-reflection layer to obtain a first mask;

[0020] S2-2, setting a second gas pressure, inputting a second gas atmosphere into the sputtering device, sputtering the upper surface of the first mask through a chromium target material, generating the first metal reflective layer, and obtaining a second mask;

[0021] S2-3, setting a third gas pressure, inputting a third gas atmosphere into the sputtering device, sputtering the upper surface of the second mask through a chromium target, generating the Fabry-Perez cavity, and obtaining a third mask;

[0022] S2-4, setting a fourth gas pressure and a second sputtering power, inputting a fourth gas atmosphere into the sputtering device, and sputtering the upper surface of the third mask through a chromium target to generate the second metal reflective layer, thereby obtaining a fourth mask;

[0023] S2-5, setting a fifth gas pressure, inputting a fifth gas atmosphere into the sputtering device, sputtering the upper surface of the fourth mask through a chromium target, generating the surface anti-reflection layer, and obtaining an original thinned mask blank.

[0024] Furthermore, the first gas atmosphere and the fourth gas atmosphere are both argon; the second gas atmosphere, the third gas atmosphere, and the fifth gas atmosphere are all mixed gas atmospheres of argon, nitrogen, and oxygen, which meet the thickness requirements of the thinned mask blank, reduce the thickness of the thinned mask blank and are up to 80% of the thickness of the traditional mask blank.

[0025] Beneficial effects of the present invention:

[0026] The thinned mask blank of the present invention has a simple structure, and utilizes the first metal reflective layer and the second metal reflective layer to form a Fabry-Perot cavity, thereby thinning the light-shielding film, thereby ensuring that the contrast and precision of the produced mask meet the production standards.

[0027] The method for making the thinned mask blank of the present invention is simple, and the process flow is simple. Only a simple process is required to realize the production of the thinned mask blank, and a substrate mask sheet with an optical density of more than 2.5 is generated. The corresponding operation difficulty is low, and it can be widely used in production lines to achieve large-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 Schematic diagram of the thinned photomask blank structure in Example 1 of the present invention; wherein, 10, transparent substrate; 1a, first metal reflective layer; 1b, second metal reflective layer; 2, 3a, back anti-reflective layer; 3b, surface anti-reflective layer;

[0030] Figure 2 is a light intensity curve diagram of the exposure light source in the Fabry-Perot chamber in Example 1 of the present invention;

[0031] Figure 3 Schematic diagram of the thinned mask blank structure in Example 1 of the present invention; wherein, 10, transparent substrate; 1a, first metal reflective layer; 1b, second metal reflective layer; 2, Fabry-Perez cavity; 3b, surface anti-reflective layer;

[0032] Figure 4 is a flow chart of a method for manufacturing a thinned photomask blank in Embodiment 1 of the present invention;

[0033] Figure 5 is a reflectivity curve diagram of a thinned photomask blank in Example 1 of the present invention;

[0034] Figure 6 is an optical density curve diagram of a thinned mask blank in Example 1 of the present invention;

[0035] Figure 7 Schematic diagram of the thinned mask blank structure in Example 2 of the present invention; wherein, 10, transparent substrate; 1a, first metal reflective layer; 2, Fabry-Perez cavity; 3b, surface anti-reflective layer;

[0036] Figure 8 is a reflectivity curve diagram of a thinned mask blank in Example 2 of the present invention;

[0037] Fig. 9 FIG. 4 is an optical density curve of a thinned mask blank in Example 2 of the present invention. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0039] Example 1

[0040] See also Figure 1 , this embodiment provides a thinned mask blank based on the Fabry-Perot interference principle, which includes a substrate for producing a mask; the substrate includes a shading film and a transparent substrate 10; the shading film includes a surface anti-reflection layer 3b, a back anti-reflection layer 3a, a Fabry-Perot cavity 2, a first metal reflection layer 1a and a second metal reflection layer 1b; wherein the film thickness of the shading film is less than 75nm, that is, the total film thickness of the surface anti-reflection layer 3b, the back anti-reflection layer 3a, the Fabry-Perot cavity 2, the first metal reflection layer 1a and the second metal reflection layer 1b is less than 75nm.

[0041] The back anti-reflection layer 3a is placed on the top of the transparent substrate 10; the first metal reflective layer 1a is placed on the top of the back anti-reflection layer 3a; the Fabry-Perot chamber 2 is placed on the top of the first metal reflective layer 1a; the second metal reflective layer 1b is placed on the top of the Fabry-Perot chamber 2; the surface anti-reflection layer 3b is placed on the top of the second metal reflective layer 1b. The surface reflectivity of the substrate is less than 20% when the exposure wavelength is 193nm and 248nm.

[0042] In this embodiment, the thickness of the back anti-reflection layer 3a is 8nm, the thickness of the first metal reflection layer 1a is 20nm, the thickness of the Fabry-Perot chamber 2 is 12nm, the thickness of the second metal reflection layer 1b is 20nm, and the thickness of the surface anti-reflection layer 3b is 10nm.

[0043] The Fabry-Perot cavity 2 is a semi-transmissive membrane; the material of the semi-transmissive membrane is chromium, oxygen and nitrogen or molybdenum, silicon, oxygen and nitrogen, the refractive index of the semi-transmissive membrane is greater than 2.3, the extinction coefficient of the semi-transmissive membrane is less than 1, and the thickness of the membrane can achieve the required low transmittance in a wide range according to the Fabry-Perot interference principle, thereby reducing the manufacturing difficulty of the Fabry-Perot cavity 2. When the refractive index of the semi-transmissive membrane is greater than 2.3 and the extinction coefficient is less than 1, the light can be reflected and transmitted multiple times in the Fabry-Perot cavity 2, thereby reducing the penetration and achieving an optical density greater than or equal to 3, effectively solving the problem of pattern shedding or position displacement, and improving the integrity, accuracy and contrast of the pattern.

[0044] The refractive index of the Fabry-Perot cavity 2 is greater than 1.5 and less than or equal to 3, and the corresponding extinction coefficient is 0.3 or less than 1.5.

[0045] In optics, a Fabry-Perot interferometer is a multi-beam interferometer composed of two parallel mirrors, and is often referred to as a Fabry-Perot resonant cavity or FP cavity, i.e., the Fabry-Perot cavity 2 of the present invention. The inner surfaces of the two mirrors facing each other have high reflectivity, and light can be reflected and interfered multiple times in the Fabry-Perot cavity 2. For the Fabry-Perot cavity 2, the significant change in the transmittance of the Fabry-Perot cavity 2 with wavelength is due to the interference of multiple reflected light between the first metal reflective layer 1a and the second metal reflective layer 1b. When the transmitted light is in phase, the Fabry-Perot cavity 2 has constructive interference, corresponding to the peak value of the transmittance of the etalon; and when the transmitted light is in antiphase, it corresponds to the minimum value of the transmittance.

[0046] Assume that the reflectivity of the first metal reflective layer 1a and the second metal reflective layer 1b are R1 and R2 respectively, the corresponding spacing is L, the corresponding electric field reflectivity is r1 and r2 respectively, and the corresponding electric field penetration is t1 and t2 respectively. When the light is reflected once in the Fabry-Perez cavity 2, the corresponding phase difference is 2πL / λ. Derived by geometric series, we get:

[0047]

[0048] Where, T represents the penetration rate of the method-cultivation cavity 2, represents the phase difference of light, and sin represents the sine function.

[0049] From the above penetration formula, we can see that only when When (N is a positive integer), such as Figure 2 As shown in FIG. 1 , the transmittance in the Fabry-Perot cavity 2 reaches the highest value, which is close to 1. When it is other values, the transmittance of the transmittance in the Fabry-Perot cavity 2 is less than the maximum value, and the minimum can be infinitely close to 0. Therefore, the film thickness of the Fabry-Perot cavity 2 can achieve the required low penetration within a large range, and the light intensity curve corresponding to the Fabry-Perot cavity 2 presents a highly flat feature, which further proves that the use of the Fabry-Perot interference principle can improve the applicability of the thinned mask blank. The thinned mask blank (mask substrate) of the present invention can be adapted to a variety of exposure light sources, thereby increasing the use scenarios of the thinned mask blank.

[0050] Since the incident light forms a standing wave in the Fabry-Perez cavity 2, the light finally dissipates in the Fabry-Perez cavity 2 and very little light penetrates the film layer, which is absorbed by the material with a high extinction number. This allows the production of a thin mask blank (mask substrate) with a thickness of less than 80% of the thickness of a conventional chrome-plated binary substrate mask plate on glass, and an optical density greater than 2.5 at a wavelength of 248nm or 193nm.

[0051] The anti-reflection layer of the thinned mask blank, ie, the surface anti-reflection layer 3 b or the back anti-reflection layer 3 a , can be formed by fixing the reaction gas ratio or gradually decreasing or increasing the reaction gas ratio.

[0052] The first metal reflective layer 1a and the second metal reflective layer 1b have the same structure and material; the first metal reflective layer 1a is made of molybdenum and silicon or chromium; when the first metal reflective layer 1a is made of molybdenum and silicon, the content of molybdenum is greater than or equal to 60%. The thickness of the first metal reflective layer 1a and the second metal reflective layer 1b is less than 12nm.

[0053] When the material of the first metal reflective layer 1a is molybdenum and silicon and the content of molybdenum is greater than or equal to 60%, due to the high reflectivity of molybdenum and the excellent light transmission characteristics of the fusion material composed of molybdenum and silicon, it is suitable for the Fabry-Perot cavity 2 with a high refractive index (>2.3) and a low extinction coefficient (<1), and the light transmittance is improved. When the material of the first metal reflective layer 1a is chromium, the reflectivity and optical stability of the thinned mask blank of the present invention can be improved, and the light absorption performance can be enhanced, thereby improving the quality of the mask pattern.

[0054] The refractive index of the surface anti-reflection layer 3b is greater than 1.5 and less than or equal to 3, the corresponding extinction coefficient is 0.3 or less than 1.5, and the corresponding film thickness is less than 20nm. The surface anti-reflection layer 3b has a surface reflectivity less than or equal to a predetermined value relative to the exposure light source, and the metal component of the first metal reflection layer 1a and the second metal reflection layer 1b is greater than the metal component of the surface anti-reflection layer 3b.

[0055] In addition, if Figure 3 As shown, the thinned mask blank may not include the back anti-reflection layer 3a, and only needs the surface anti-reflection layer 3b, and the same purpose of the invention can be achieved.

[0056] like Figure 4 As shown, a method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle includes:

[0057] S1. Clean the transparent substrate 10. The length, width and thickness of the transparent substrate 10 are 6 inches, 6 inches and 0.25 inches respectively.

[0058] The step of cleaning the transparent substrate 10 includes:

[0059] S1-1, irradiate the transparent substrate 10 with ultrasound or ultraviolet rays, and perform initial cleaning of the transparent substrate 10 with ultrapure water or functional water; since there are particles on the surface of the transparent substrate 10 or the thin film formed on the transparent substrate 10, the particles on the transparent substrate 10 can be removed by ultrapure water or functional water when the transparent substrate 10 is irradiated with ultrasound or ultraviolet rays, or one or both of ultrapure water and functional water can be used for removal. Among them, ultrapure water is ultrapure water containing a surfactant, and functional water is ultrapure water containing multiple gases such as ozone gas and hydrogen.

[0060] S1-2. The transparent substrate 10 is cleaned for a second time using a sulfur-free cleaning method. The transparent substrate 10 also has defects caused by organic compounds, so a mixed solution of sulfuric acid and hydrogen peroxide is generally selected for cleaning. Because the surface of the transparent substrate 10 is acidic after the initial cleaning, it needs to be rinsed and neutralized with alkaline ammonia water (ammonia plus hydrogen peroxide or a mixed solution). However, since alkaline ammonia water cannot completely remove sulfate ions on the surface of the substrate, sulfate ions remain on the surface, which in turn affects the formed shading film, resulting in poor adhesion, pattern linearity and resolution of the shading film. In addition, when ions including sulfuric acid and ammonium salts are used to clean the mask, if the thinned mask blank is exposed to short-wavelength ultraviolet rays, such as ultraviolet rays with a wavelength of 248 or 193nm, haze pollution may be generated, so a sulfur-free cleaning method is used to clean the transparent substrate 10 for a second time.

[0061] S2, placing the cleaned transparent substrate 10 in a sputtering device for sputtering, sequentially forming a back anti-reflection layer 3a, a first metal reflection layer 1a, a Fabry-Perot cavity 2, a second metal reflection layer 1b, and a surface anti-reflection layer 3b, to obtain an original thinned mask blank;

[0062] The cleaned transparent substrate 10 is placed in a sputtering device for sputtering, and a back anti-reflection layer 3a, a first metal reflection layer 1a, a Fabry-Perot cavity 2, a second metal reflection layer 1b, and a surface anti-reflection layer 3b are sequentially formed to obtain an original thinned mask blank, including:

[0063] S2-1, placing the cleaned transparent substrate 10 in a sputtering device, setting a first gas pressure and a first sputtering power, inputting a first gas atmosphere into the sputtering device, and sputtering the upper surface of the cleaned transparent substrate 10 through a chromium target to generate a back anti-reflection layer 3a with a thickness of 8 nm, thereby obtaining a first mask;

[0064] The first gas pressure is 0.05 Pa, the first sputtering power is 1.5 KW, and the first gas atmosphere is argon gas; wherein the flow rate of argon gas is 50 sccm.

[0065] S2-2, setting a second gas pressure, inputting a second gas atmosphere into the sputtering device, sputtering the upper surface of the first mask through a chromium target, generating a first metal reflective layer 1a with a thickness of 20 nm, and obtaining a second mask;

[0066] The second gas pressure is 0.05 Pa, and the second gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen; wherein the flow rate of argon is 10 sccm, the flow rate of nitrogen is 31 sccm, and the flow rate of oxygen is 5 sccm.

[0067] S2-3, setting a third gas pressure, inputting a third gas atmosphere into the sputtering device, sputtering the upper surface of the second mask through a chromium target, generating a Fabry-Perot cavity 2 with a thickness of 12 nm, and obtaining a third mask;

[0068] The third gas pressure is 0.05 Pa, and the third gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen; wherein the flow rate of argon is 10 sccm, the flow rate of nitrogen is 31 sccm, and the flow rate of oxygen is 5 sccm.

[0069] S2-4, setting a fourth gas pressure and a second sputtering power, inputting a fourth gas atmosphere into the sputtering device, and sputtering the upper surface of the third mask through a chromium target to generate a second metal reflective layer 1b with a thickness of 20 nm, thereby obtaining a fourth mask;

[0070] The fourth gas pressure is 0.05 Pa, the second sputtering power is 1.5 KW, and the fourth gas atmosphere is argon gas; wherein the flow rate of argon gas is 50 sccm.

[0071] S2-5, setting a fifth gas pressure, inputting a fifth gas atmosphere into the sputtering device, sputtering the upper surface of the fourth mask through a chromium target, generating a surface anti-reflection layer 3b with a thickness of 10 nm, and obtaining an original thinned mask blank.

[0072] The fifth gas pressure is 0.05 Pa, and the fifth gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen; wherein the flow rate of argon is 10 sccm, the flow rate of nitrogen is 31 sccm, and the flow rate of oxygen is 5 sccm.

[0073] S3. Using a hot plate annealing device, heat-treat the original thinned mask blank at 2000° C. for 10 minutes to obtain a thinned mask blank.

[0074] The thinned mask blank (mask substrate) in the embodiment has a reduced film thickness, so that the change in the deflection within a 142 mm square of the central portion of the surface of the corresponding transparent substrate 10 is less than 0.2 um in absolute value.

[0075] like Figure 5 and Figure 6 As shown, when the wavelength of the incident light is 193 nm, the reflectivity of the photomask substrate of this embodiment is less than 20%, and the optical density is greater than 3, and it can be used to manufacture ArF photomask substrates. Figure 5 and Figure 6 In FIG. 1 , R represents the reflectivity of the photomask substrate, and OD represents the optical density of the photomask substrate.

[0076] In summary, the thinned mask blank of the present invention has a simple structure, and uses the first metal reflective layer 1a and the second metal reflective layer 1b to form a method-pei cavity 2, thereby achieving thinning of the light-shielding film, and supporting the minimum feature size, linearity and through-hole spacing requirements required for the substrate mask plate. The manufacturing method of the thinned mask blank of the present invention is simple, and the process flow is simple. Only a simple process is required to realize the manufacturing of the thinned mask blank, and generate a substrate mask sheet with an optical density of more than 3. The corresponding operation difficulty is low, and it can be widely used in production lines to achieve large-scale mass production.

[0077] Example 2

[0078] like Figure 7 As shown, this embodiment provides a thinned mask blank based on the Fabry-Perot interference principle, which includes a substrate for producing a mask; the substrate includes a shading film and a transparent substrate 10; the shading film includes a surface anti-reflection layer 3b, a Fabry-Perot cavity 2, and a first metal reflective layer 1a.

[0079] The first metal reflective layer 1a is placed on the top of the transparent substrate 10; the Fabry-Perot chamber 2 is placed on the top of the first metal reflective layer 1a; the Fabry-Perot chamber 2 is placed on the top of the first metal reflective layer 1a; the surface anti-reflection layer 3b is placed on the top of the Fabry-Perot chamber 2.

[0080] In this embodiment, the film thickness of the first metal reflective layer 1a is 32nm, the film thickness of the Fabry-Perot cavity 2 is 12nm, the film thickness of the surface anti-reflective layer 3b is 40nm, and the remaining settings of the thinned mask blank and its surface anti-reflective layer 3b, the Fabry-Perot cavity 2, and the first metal reflective layer 1a are the same as the thinned mask blank and its surface anti-reflective layer 3b, the Fabry-Perot cavity 2, and the first metal reflective layer 1a in Example 1.

[0081] A method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle, comprising:

[0082] A1. Clean the transparent substrate 10. The length, width and thickness of the transparent substrate 10 are 6 inches, 6 inches and 0.25 inches respectively.

[0083] The step of cleaning the transparent substrate 10 includes:

[0084] A1-1. The transparent substrate 10 is irradiated with ultrasound or ultraviolet rays, and the transparent substrate 10 is initially cleaned with ultrapure water or functional water. Since particles exist on the surface of the transparent substrate 10 or the thin film formed on the transparent substrate 10, the particles on the transparent substrate 10 can be removed by ultrapure water or functional water when the transparent substrate 10 is irradiated with ultrasound or ultraviolet rays, or one or both of ultrapure water and functional water can be used for removal. The ultrapure water is ultrapure water containing a surfactant, and the functional water is ultrapure water containing multiple gases such as ozone gas and hydrogen gas.

[0085] A1-2. The transparent substrate 10 is cleaned for a second time using a sulfur-free cleaning method. The transparent substrate 10 also has defects caused by organic compounds, so a mixed solution of sulfuric acid and hydrogen peroxide is generally selected for cleaning. Because the surface of the transparent substrate 10 is acidic after the initial cleaning, it needs to be rinsed and neutralized with alkaline ammonia water (ammonia plus hydrogen peroxide or a mixed solution). However, since alkaline ammonia water cannot completely remove sulfate ions on the surface of the substrate, sulfate ions remain on the surface, which in turn affects the formed shading film, resulting in poor adhesion, pattern linearity and resolution of the shading film. In addition, when ions including sulfuric acid and ammonium salts are used to clean the mask, if the thinned mask blank is exposed to short-wavelength ultraviolet rays, such as ultraviolet rays with a wavelength of 248 or 193nm, haze pollution may be generated, so a sulfur-free cleaning method is used to clean the transparent substrate 10 for a second time.

[0086] A2. Place the cleaned transparent substrate 10 in a sputtering device for sputtering to sequentially generate a first metal reflective layer 1a, a Fabry-Perot cavity 2, and a surface anti-reflective layer 3b to obtain an original thinned mask blank.

[0087] The cleaned transparent substrate 10 is placed in a sputtering device for sputtering, and the first metal reflective layer 1a, the Fabry-Perot cavity 2, and the surface anti-reflective layer 3b are sequentially formed to obtain an original thinned mask blank, including:

[0088] A2-1. Place the cleaned transparent substrate 10 in a sputtering device, set the sixth gas pressure and the third sputtering power, input the sixth gas atmosphere into the sputtering device, and sputter the upper surface of the cleaned transparent substrate 10 through a chromium target to generate a first metal reflective layer 1a with a thickness of 32 nm to obtain a fifth mask.

[0089] The sixth gas pressure is 0.05 Pa, the sixth gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen, and the third sputtering power is 1.5 KW; wherein, the flow rate of argon is 10 sccm, the flow rate of nitrogen gradually decreases from 31 sccm to 0 sccm as the film thickness of the first metal reflective layer 1a increases during film formation, and the flow rate of oxygen is 5 sccm; the thin film corresponding to the first metal reflective layer 1a also has the functions of the back anti-reflection layer 3a and the first metal reflective layer 1a in Example 1 because the flow rate of nitrogen gradually decreases from 31 sccm to 0 sccm as the thickness increases during film formation.

[0090] A2-2. Set the seventh gas pressure and the fourth sputtering power, input the seventh gas atmosphere into the sputtering device, and sputter the upper surface of the fifth mask by using a target material made of molybdenum and silicon to generate a Fabry-Perot cavity 2 with a thickness of 12 nm, thereby obtaining a sixth mask; the molar ratio of molybdenum to silicon in the target material made of molybdenum and silicon is 10:90.

[0091] The seventh gas pressure is 0.05Pa, the seventh gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen, and the fourth sputtering power is 1.5KW; wherein, the flow rate of argon is 10sccm, the flow rate of nitrogen is 31sccm, and the flow rate of oxygen is 5sccm; wherein, the Fabry-Perot chamber 2 of this embodiment has a transmittance of 20% below a wavelength of 248nm.

[0092] A2-3. Set the eighth gas pressure and the fifth sputtering power, input the eighth gas atmosphere into the sputtering device, and sputter the upper surface of the sixth mask through a chromium target to generate a surface anti-reflection layer 3b with a thickness of 40 nm to obtain an original thinned mask blank.

[0093] The eighth gas pressure is 0.05Pa, the eighth gas atmosphere is a mixed gas atmosphere of argon, nitrogen and oxygen, and the fifth sputtering power is 1.5KW; wherein, the flow rate of argon is 10sccm, the flow rate of nitrogen gradually increases from 0sccm to 31sccm as the film thickness of the surface anti-reflection layer 3b increases during film formation, and the flow rate of oxygen is 5sccm; the thin film corresponding to the surface anti-reflection layer 3b also has the functions of the surface anti-reflection layer 3b and the second metal reflective layer 1b in Example 1 because the flow rate of nitrogen gradually increases from 0sccm to 31sccm as the thickness increases during film formation.

[0094] A3. Use a hot plate annealing device to perform heat treatment on the original thinned mask blank at 2000°C for 10 minutes to obtain a thinned mask blank.

[0095] like Figure 8 and Fig. 9 As shown, when the wavelength of the incident light is 193nm or 248nm, the reflectivity of the photomask substrate of this embodiment is less than 20%, and the optical density is greater than 3, and it can be used to make ArF photomask substrates and KrF photomask substrates. Figure 8 and Fig. 9 In FIG. 1 , R represents the reflectivity of the photomask substrate, and OD represents the optical density of the photomask substrate.

[0096] In summary, the structure of the thinned mask blank of the present invention is simple. By controlling the content of the gas atmosphere of the sputtering device, the surface anti-reflection layer 3b, the Fabry-Perez cavity 2, and the first metal reflective layer 1a are formed, which can achieve the thinning of the light-shielding film, reduce the process steps, and further improve the yield of the thinned mask blank. The method for making the thinned mask blank of the present invention is simple, and only a simple process is required to achieve the production of the thinned mask blank, and generate a substrate mask sheet with an optical density of more than 3. The corresponding operation difficulty is low, and large-scale mass production is achieved.

[0097] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A thinned mask blank based on the Fabry-Perot interference principle, characterized in that: The invention comprises a substrate for producing a photomask; the substrate comprises a light shielding film and a transparent substrate; the light shielding film comprises a surface anti-reflection layer, a back anti-reflection layer, a Fabry-Perot cavity, a first metal reflection layer and a second metal reflection layer; The back anti-reflection layer is placed on the top of the transparent substrate; the first metal reflective layer is placed on the top of the back anti-reflection layer; the Fabry-Perregaux cavity is placed on the top of the first metal reflective layer; the second metal reflective layer is placed on the top of the Fabry-Perregaux cavity; and the surface anti-reflection layer is placed on the top of the second metal reflective layer.

2. The thinned mask blank based on the Fabry-Perot interference principle according to claim 1, characterized in that: The Fabry-Perez cavity is a semi-permeable membrane; the material of the semi-permeable membrane is chromium, oxygen and nitrogen or molybdenum, silicon, oxygen and nitrogen, the refractive index of the semi-permeable membrane is greater than 2.3, and the extinction coefficient of the semi-permeable membrane is less than 1.

3. The thinned mask blank based on the Fabry-Perot interference principle according to claim 1, characterized in that: The structures and materials of the first metal reflective layer and the second metal reflective layer are the same; the material of the first metal reflective layer is molybdenum and silicon or chromium; when the material of the first metal reflective layer is molybdenum and silicon, the content of molybdenum is greater than or equal to 60%.

4. A method for manufacturing a thinned mask blank based on the Fabry-Perot interferometer principle, for realizing the thinned mask blank based on the Fabry-Perot interferometer principle as claimed in any one of claims 1 to 3, characterized in that: include: S1. Cleaning the transparent substrate; S2, placing the cleaned transparent substrate in a sputtering device for sputtering, sequentially forming a back anti-reflection layer, a first metal reflection layer, a Fabry-Perez cavity, a second metal reflection layer, and a surface anti-reflection layer, to obtain an original thinned mask blank; S3, using a hot plate annealing device to perform heat treatment on the original thinned mask blank to obtain a thinned mask blank.

5. The method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle according to claim 4, characterized in that: The step of cleaning the transparent substrate comprises: S1-1, irradiating the transparent substrate with ultrasound or ultraviolet rays, and initially cleaning the transparent substrate with ultrapure water or functional water; S1-2, performing secondary cleaning on the transparent substrate using a sulfur-free cleaning method to obtain the cleaned transparent substrate.

6. The method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle according to claim 4, characterized in that: The cleaned transparent substrate is placed in a sputtering device for sputtering to sequentially generate a back anti-reflection layer, a first metal reflection layer, a Fabry-Perez cavity, a second metal reflection layer, and a surface anti-reflection layer to obtain an original thinned mask blank, including: S2-1, placing the cleaned transparent substrate in a sputtering device, setting a first gas pressure and a first sputtering power, inputting a first gas atmosphere into the sputtering device, and sputtering the upper surface of the cleaned transparent substrate through a chromium target to generate the back anti-reflection layer to obtain a first mask; S2-2, setting a second gas pressure, inputting a second gas atmosphere into the sputtering device, sputtering the upper surface of the first mask through a chromium target material, generating the first metal reflective layer, and obtaining a second mask; S2-3, setting a third gas pressure, inputting a third gas atmosphere into the sputtering device, sputtering the upper surface of the second mask through a chromium target, generating the Fabry-Perez cavity, and obtaining a third mask; S2-4, setting a fourth gas pressure and a second sputtering power, inputting a fourth gas atmosphere into the sputtering device, and sputtering the upper surface of the third mask through a chromium target to generate the second metal reflective layer, thereby obtaining a fourth mask; S2-5, setting a fifth gas pressure, inputting a fifth gas atmosphere into the sputtering device, sputtering the upper surface of the fourth mask through a chromium target, generating the surface anti-reflection layer, and obtaining an original thinned mask blank.

7. The method for manufacturing a thinned mask blank based on the Fabry-Perot interference principle according to claim 4, characterized in that: The first gas atmosphere and the fourth gas atmosphere are both argon; the second gas atmosphere, the third gas atmosphere, and the fifth gas atmosphere are all mixed gas atmospheres of argon, nitrogen, and oxygen.

Images