JP2021181398A - Glass substrate for euvl, method for manufacturing the same, mask blank for euvl and method for manufacturing the same - Google Patents

Abstract

To provide a technique capable of suppressing the expansion of a scratch formed on the end surface or notch surface of a glass substrate for EUVL.SOLUTION: A glass substrate for EUVL includes: a first rectangular main surface; a rectangular second main surface oppositely facing the first main surface; four end surfaces perpendicular to the first main surface and the second main surface; four first chamfering surfaces formed in boundaries between the first main surface and the end surfaces; and four second chamfering surfaces formed in boundaries between the second main surface and the end surfaces. The glass substrate for EUVL is formed of TiO2 containing quartz glass, and the end surfaces including fluorine (F) and elements (A) except the fluorine forming a gas cluster with the fluorine satisfy the formula (1) and the formula (2) in the specification.SELECTED DRAWING: Figure 12

Description

The present disclosure relates to a glass substrate for EUV, a method for manufacturing the same, a mask blank for EUV, and a method for manufacturing the same.

Traditionally, photolithography technology has been used in the manufacture of semiconductor devices. In the photolithography technique, the photomask pattern is irradiated with light by an exposure apparatus, and the photomask pattern is transferred to the resist film.

Recently, in order to enable transfer of fine patterns, the use of short wavelength exposure light, for example, ArF excimer laser light, EUV (Extreme Ultra-Violet) light, and the like has been studied.

Here, EUV light includes soft X-rays and vacuum ultraviolet light, and specifically, light having a wavelength of about 0.2 nm to 100 nm. At present, EUV light having a wavelength of about 13.5 nm is mainly studied as exposure light.

Patent Document 1 describes a method for producing a mask blank for EUVL (Extreme Ultra-Violet Lithography). The EUV mask blank includes a glass substrate, a reflective film formed on the glass substrate, and an absorbent film formed on the reflective film.

The EUV mask blank is required to have a high flatness in order to improve the transfer accuracy of fine patterns. Since the flatness of the EUV mask blank is mainly determined by the flatness of the glass substrate which is the substrate, high flatness is required for the glass substrate.

Therefore, in order to improve the flatness of the glass substrate, an etching step of irradiating the main surface of the glass substrate with a beam-shaped gas cluster is performed. The main surface of the glass substrate is locally etched and flattened by gas clusters.

Patent Document 1 discloses a technique of driving fluorine or chlorine from the main surface of a glass substrate to a depth of about 100 nm by irradiating a gas cluster. According to this technique, a compressive stress layer is generated on the main surface of the glass substrate, and the strength of the main surface of the glass substrate is improved.

Japanese Unexamined Patent Publication No. 2009-155170

By the way, the EUV glass substrate is subjected to a polishing step, an inspection step, a film forming step, and the like after the etching step of irradiating the gas cluster. These processes are collectively called a post-process.

In the post-process, the end face of the glass substrate is pressed against a holder, a positioning tool, or the like. Therefore, the end face is easily scratched. In addition, instead of the end face, or in addition to the end face, the notch surface may be pressed against the holder or the positioning tool.

The notch surface is formed at an angle to the main surface so as to scrape off the corners of the two adjacent end faces and the main surface. The notch surface indicates the orientation of the glass substrate, and the glass substrate is installed in various devices and pressed against a holder, a positioning tool, or the like so that the orientation of the glass substrate is a desired orientation.

The notch surface may be omitted.

It is inevitable that the end face or notch surface of the glass substrate will be scratched. However, if the scratches extend and large defects occur, the glass substrate is discarded as a defective product. Therefore, the yield is lowered.

One aspect of the present disclosure provides a technique capable of suppressing the extension of scratches formed on the end face or notch surface of a glass substrate for EUV.

The EUVL glass substrate according to one aspect of the present disclosure includes a rectangular first main surface, a rectangular second main surface opposite to the first main surface, the first main surface, and the second main surface. Four end faces perpendicular to the main surface, four first chamfered surfaces formed at the boundary between the first main surface and the end face, and formed at the boundary between the second main surface and the end face. It has four second chamfers and four. The EUV glass substrate is made of quartz glass containing _{TiO 2.} The end face contains fluorine (F) and an element (A) other than fluorine that forms a gas cluster together with fluorine, and satisfies the following formulas (1) and (2).

上記式（１）中、Ｄ１（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＦの強度であり、ｘは前記端面からの深さ（単位：ｎｍ）、ａ１ｘ+ｂ１はｘが２００以上４００以下の範囲におけるＤ１（ｘ）を最小二乗法で近似した直線である。上記式（２）中、Ｄ２（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＡの強度であり、ｘは前記端面からの深さ（単位：ｎｍ）、ａ２ｘ+ｂ２はｘが２００以上４００以下の範囲におけるＤ２（ｘ）を最小二乗法で近似した直線である。

In the above formula (1), D1 (x) is the intensity of F normalized by the intensity of Si measured by TOF-SIMS, and x is the depth from the end face (unit: nm), a1x +. b1 is a straight line obtained by approximating D1 (x) in the range where x is 200 or more and 400 or less by the least squares method. In the above formula (2), D2 (x) is the intensity of A normalized by the intensity of Si measured by TOF-SIMS, and x is the depth from the end face (unit: nm), a2x +. b2 is a straight line obtained by approximating D2 (x) in the range where x is 200 or more and 400 or less by the least squares method.

The EUVL glass substrate according to another aspect of the present disclosure includes a rectangular first main surface, a rectangular second main surface opposite to the first main surface, the first main surface, and the above. At the boundary between the second main surface and the end surface, the four end faces perpendicular to the second main surface, the four first chamfered surfaces formed at the boundary between the first main surface and the end surface, and the boundary between the second main surface and the end surface. Four second chamfered surfaces formed, and one or more notch surfaces formed obliquely to the first main surface so as to scrape off the corners of two adjacent end surfaces and the first main surface. And have. The EUV glass substrate is made of quartz glass containing _{TiO 2.} The notch surface contains fluorine (F) and an element (A) other than fluorine that forms a gas cluster together with fluorine, and satisfies the following formulas (3) and (4).

上記式（３）中、Ｄ３（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＦの強度であり、ｘは前記ノッチ面からの深さ（単位：ｎｍ）、ａ３ｘ+ｂ３はｘが２００以上４００以下の範囲におけるＤ３（ｘ）を最小二乗法で近似した直線であり、上記式（４）中、Ｄ４（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＡの強度であり、ｘは前記ノッチ面からの深さ（単位：ｎｍ）、ａ４ｘ+ｂ４はｘが２００以上４００以下の範囲におけるＤ４（ｘ）を最小二乗法で近似した直線である。

In the above formula (3), D3 (x) is the intensity of F standardized by the intensity of Si measured by TOF-SIMS, and x is the depth from the notch surface (unit: nm), a3x. + b3 is a straight line obtained by approximating D3 (x) in the range of x of 200 or more and 400 or less by the least squares method. It is the intensity of A standardized by the intensity, x is the depth from the notch surface (unit: nm), and a4x + b4 approximates D4 (x) in the range where x is 200 or more and 400 or less by the least squares method. It is a straight line.

According to one aspect of the present disclosure, it is possible to suppress the extension of scratches formed on the end surface or notch surface of the EUV glass substrate.

FIG. 1 is a flowchart showing a method for manufacturing an EUV mask blank according to an embodiment. FIG. 2 is a cross-sectional view showing an example of the glass substrate used in S101 of FIG. FIG. 3 is a plan view showing an example of the glass substrate of FIG. FIG. 4 is a cross-sectional view showing a mask blank for EUV according to an embodiment. FIG. 5 is a cross-sectional view showing an example of a EUV photomask. FIG. 6 is a cross-sectional view showing a processing apparatus according to an embodiment. FIG. 7 is an enlarged cross-sectional view showing the glass substrate of FIG. 6 and its peripheral parts. FIG. 8 is a diagram showing a glass substrate and its peripheral components as viewed from the irradiation direction of the gas cluster of FIG. 7. FIG. 9 is a view of the clamp and spacer of FIG. 7 as viewed from another direction. FIG. 10 is a schematic diagram showing an example of a collision of a gas cluster with a glass substrate. FIG. 11 is a diagram showing irradiation of a gas cluster to the end face of the glass substrate of Example 1. FIG. 12 is a diagram showing the distribution of F intensity / Si intensity in the depth direction obtained by measuring the end face of the glass substrate of Example 1 by TOF-SIMS. FIG. 13 is a diagram showing the distribution of C intensity / Si intensity in the depth direction obtained by measuring the end face of the glass substrate of Example 1 by TOF-SIMS. FIG. 14 is a diagram comparing the hardness of the end faces of the glass substrate of Example 1 before and after irradiation with gas clusters. FIG. 15 is a diagram showing the distribution of F intensity / Si intensity in the depth direction obtained by measuring the notch surface of the glass substrate of Example 2 by TOF-SIMS. FIG. 16 is a diagram showing the distribution of C intensity / Si intensity in the depth direction obtained by measuring the notch surface of the glass substrate of Example 2 by TOF-SIMS.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations may be designated by the same reference numerals and description thereof may be omitted. In the specification, "~" indicating a numerical range means that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.

As shown in FIG. 1, a method for producing a mask blank for EUVL (Extreme Ultra-Violet Lithography) includes S101 to S107. A glass substrate is used to manufacture the mask blank. The glass of the glass substrate is preferably quartz glass containing _{TiO 2.} Quartz glass has a smaller coefficient of linear expansion and smaller dimensional change due to temperature changes than general soda lime glass. Quartz glass, a SiO ₂ 80 wt% to 95 wt%, may include TiO ₂ 4 wt% to 17 wt%. When the TiO ₂ content is 4% by mass to 17% by mass, the coefficient of linear expansion near room temperature is substantially zero, and there is almost no dimensional change near room temperature. Quartz glass may contain a third component or impurities other than _{SiO 2} and TiO _2. As such quartz glass, for example, Corning's ULE (registered trademark) 7973 series may be used.

As shown in FIGS. 2 and 3, the glass substrate 2 has a first main surface 21, a second main surface 22, four end surfaces 23, four first chamfered surfaces 24, and four second surfaces. It includes a chamfer surface 25 and three notch surfaces 26. The first main surface 21 has a rectangular shape. In the present specification, the rectangular shape includes a shape in which the corners are chamfered. Also, the rectangle includes a square. The second main surface 22 is in the opposite direction to the first main surface 21. The second main surface 22 is also rectangular like the first main surface 21. The end surface 23 is perpendicular to the first main surface 21 and the second main surface 22. The first chamfered surface 24 is formed at the boundary between the first main surface 21 and the end surface 23. The second chamfered surface 25 is formed at the boundary between the second main surface 22 and the end surface 23. The first chamfered surface 24 and the second chamfered surface 25 are so-called C chamfered surfaces in the present embodiment, but may be R chamfered surfaces. The notch surface 26 is formed obliquely with respect to the first main surface 21 so as to scrape off the corners of the two adjacent end surfaces 23 and the first main surface 21. The notch surface 26 indicates the orientation of the glass substrate 2, and the glass substrate 2 is installed in various devices so that the orientation of the glass substrate 2 is a desired orientation. The number of notch surfaces 26 is three in the present embodiment, but may be one or more, and is not particularly limited. For example, even if the number of notch surfaces 26 is four, the orientation of the glass substrate 2 can be determined if the sizes of the notch surfaces 26 are different. The notch surface 26 may be omitted, and the number of notch surfaces 26 may be zero.

The first main surface 21 of the glass substrate 2 has a quality assurance region 27 shown by a dot pattern in FIG. The quality assurance region 27 is an region processed to a desired flatness by S101 to S104. The quality assurance region 27 is an region excluding the peripheral region 28 in which the distance L from the end surface 23 is, for example, 5 mm or less when viewed from the direction orthogonal to the first main surface 21. Although not shown, the second main surface 22 of the glass substrate 2 also has a quality assurance region and a peripheral region, similarly to the first main surface 21.

First, in S101 of FIG. 1, the first main surface 21 and the second main surface 22 of the glass substrate 2 are polished. The first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine. In S101, the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, cerium oxide particles. The first main surface 21 and the second main surface 22 may be polished a plurality of times with abrasives of different materials or particle sizes.

The abrasive used in S101 is not limited to cerium oxide particles. For example, the abrasive used in S101 may be silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, or the like.

Next, in S102 of FIG. 1, the surface shapes of the first main surface 21 and the second main surface 22 of the glass substrate 2 are measured. For the measurement of the surface shape, for example, a non-contact type measuring machine such as a laser interference type is used so that the surface is not damaged. The measuring machine measures the surface shapes of the quality assurance area 27 of the first main surface 21 and the quality assurance area 27 of the second main surface 22.

Next, in S103 of FIG. 1, the first main surface 21 and the second main surface 22 of the glass substrate 2 are processed by a beam-shaped gas cluster in order to improve the flatness with reference to the measurement result of S102. The first main surface 21 and the second main surface 22 are sequentially etched by the gas cluster. The order may be either first and is not particularly limited.

The gas cluster is ionized by thermionic collisions, subsequently accelerated by an electric field, and after neutralization, is irradiated towards the first main surface 21 or the second main surface 22. Due to the collision of the gas cluster, the first main surface 21 or the second main surface 22 is locally etched and flattened. The details of S103 will be described later.

Next, in S104 of FIG. 1, the first main surface 21 and the second main surface 22 of the glass substrate 2 are finish-polished. The first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine. In S104, the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, colloidal silica particles.

Next, in S105 of FIG. 1, the reflective film 3 shown in FIG. 4 is formed in the quality assurance region 27 of the first main surface 21 of the glass substrate 2. The reflective film 3 reflects EUV light. The reflective film 3 may be, for example, a multilayer reflective film in which high refractive index layers and low refractive index layers are alternately laminated. The high refractive index layer is formed of, for example, silicon (Si), and the low refractive index layer is formed of, for example, molybdenum (Mo). As a film forming method for the reflective film 3, for example, a sputtering method such as an ion beam sputtering method or a magnetron sputtering method is used.

Next, in S106 of FIG. 1, the absorption film 4 shown in FIG. 4 is formed on the reflective film 3 formed in S105. The absorbent film 4 absorbs EUV light. The absorption film 4 is formed of, for example, a single metal containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd), an alloy, a nitride, an oxide, an acid nitride, or the like. As a film forming method for the absorbent film 4, for example, a sputtering method is used.

Finally, in S107 of FIG. 1, the conductive film 5 shown in FIG. 4 is formed in the quality assurance region of the second main surface 22 of the glass substrate 2. The conductive film 5 is used for electrostatically adsorbing a photomask with an electrostatic chuck of an exposure apparatus. The conductive film 5 is formed of, for example, chromium nitride (CrN) or the like. As a film forming method of the conductive film 5, for example, a sputtering method is used. Although S107 is carried out after S105 and S106 in this embodiment, it may be carried out before S105 and S106.

The arrangement of the reflective film 3 and the conductive film 5 may be reversed. That is, the conductive film 5 may be formed in the quality assurance region 27 of the first main surface 21 of the glass substrate 2, and the reflective film 3 may be formed in the quality assurance region of the second main surface 22 of the glass substrate 2. The absorbent film 4 is formed on the reflective film 3.

From S101 to S107, the EUV mask blank 1 shown in FIG. 4 is obtained. The EUV mask blank 1 includes a glass substrate 2, a reflective film 3, an absorbing film 4, and a conductive film 5. The EUV mask blank 1 does not have to include the conductive film 5. Further, the EUV mask blank 1 may include yet another film.

For example, the EUV mask blank 1 may further include a low reflection film. The low-reflection film is formed on the absorption film 4. The low-reflection film is used for inspecting the opening pattern 41 of the absorption film 4 shown in FIG. 5, and has lower reflection characteristics than the absorption film 4 with respect to the inspection light. The low-reflection film is formed of, for example, TaON or TaO. As a method for forming a low-reflection film, for example, a sputtering method is used.

Further, the EUV mask blank 1 may further include a protective film. The protective film is formed between the reflective film 3 and the absorbing film 4. The protective film protects the reflective film 3 so that the reflective film 3 is not etched when the absorbent film 4 is etched to form the opening pattern 41 in the absorbent film 4. The protective film is formed of, for example, Ru, Si, TiO ₂ or the like. As a method for forming a protective film, for example, a sputtering method is used.

As shown in FIG. 5, the EUV photomask is obtained by forming an opening pattern 41 on the absorption film 4. A photolithography method and an etching method are used to form the opening pattern 41. Therefore, the resist film used for forming the opening pattern 41 may be included in the EUV mask blank 1.

Next, with reference to FIG. 6, the processing apparatus used in S103 of FIG. 1 will be described. The processing apparatus 100 is a so-called GCIB (Gas Cruster Ion Beam) processing apparatus.

The processing apparatus 100 includes a vacuum container 101. The vacuum vessel 101 has a nozzle chamber 102, an ionization / acceleration chamber 103, and a processing chamber 104. The three chambers 102, 103, 104 are connected to each other to form a passage for the gas cluster. The three chambers 102, 103, 104 are exhausted by the three vacuum pumps 105, 106, 107 and maintained at the desired degree of vacuum. The number of chambers and the number of vacuum pumps are not particularly limited.

The processing apparatus 100 includes a generation unit 110. The generation unit 110 generates a gas cluster. The generation unit 110 includes, for example, a raw material tank 111, a pressure controller 113, a supply pipe 114, and a nozzle 116. The raw material tank 111 stores the raw material gas (for example, CF ₄ gas). The pressure controller 113 controls the supply pressure of the raw material gas supplied from the raw material tank 111 to the nozzle 116 via the supply pipe 114. The nozzle 116 is provided in the nozzle chamber 102 and injects a raw material gas into a vacuum to form a supersonic gas jet 118.

The raw material gas is cooled by adiabatic expansion in the gas jet 118. As a result, a portion of the gas jet 118 condenses into a gas cluster, each of which is an aggregate of several to several thousand atoms or molecules. Many gas clusters are included near the center of the flow of the gas jet 118. Therefore, according to schema 119, the gas cluster can be efficiently sent out by passing only the vicinity of the center of the flow of the gas jet 118.

The raw material gas is _{not limited to CF 4} gas, but is CHF ₃ gas, CH ₂ F ₂ gas, C ₂ F ₆ gas, BF ₃ gas, NF ₃ gas, SF ₆ gas, SeF ₆ gas, and TeF ₆ gas. , Or WF ₆ gas or the like. Although details will be described later, among these gases, CF ₄ gas, CHF ₃ gas, or _CH 2 _{F 2} gas is preferable. A plurality of gases may be selected from these gases, and a mixed gas may be used as a raw material gas.

The processing apparatus 100 includes an ionization unit 120. The ionization unit 120 ionizes at least a part of the gas cluster in the gas jet 118. The ionization unit 120 includes, for example, one or more thermal filaments 124 and a cylindrical electrode 126. Hot filament 124, to generate heat by the power (voltage _{V F)} from the power source 125, which emits thermal electrons. The cylindrical electrode 126 accelerates thermions emitted from the thermal filament 124 and causes the accelerated thermions to collide with the gas cluster. Collision between an electron and a gas cluster emits an electron from a part of the gas cluster, and these gas clusters are positively ionized. In some cases, two or more electrons are emitted and multivalent ionization occurs. _A voltage VA from the power supply 127 is applied between the cylindrical electrode 126 and the thermal filament 124. This voltage _VA (electric field) accelerates thermions and collides with gas clusters.

The processing apparatus 100 includes an acceleration unit 130. The acceleration unit 130 accelerates the gas cluster ionized by the ionization unit 120 to form the GCIB 128. The acceleration unit 130 includes, for example, a first electrode 132 and a second electrode 134. The second electrode 134 is grounded, and a positive voltage Vs is applied to the first electrode 132 from the power supply 135. The first electrode 132 and the second electrode 134 form an electric field that accelerates the positively ionized gas cluster. The accelerated gas cluster is withdrawn as GCIB 128 from the opening of the second electrode 134. _{The power supply 136 supplies an acceleration voltage V Acc} that biases the ionization unit 120 to the first electrode 132 and the second electrode 134 so that the total GCIB acceleration potential becomes equal _{to V Acc.} V _Acc, for example 1KV～200kV, preferably 1KV～70kV.

The processing apparatus 100 may include a neutralization portion (not shown). The neutralization section neutralizes the GCIB 128 formed by the acceleration section 130 to form a neutral gas cluster. Since the neutral gas cluster is irradiated on the glass substrate 2, it is possible to prevent the glass substrate 2 from being charged. Even if the glass substrate 2 is irradiated with positively ionized gas clusters, the glass substrate 2 can be etched.

The processing apparatus 100 includes an irradiation unit 150. The irradiation unit 150 irradiates the glass substrate 2 with the beam-shaped gas cluster 129 and locally etches the glass substrate 2. The half width of the beam intensity distribution of the gas cluster 129 is, for example, 1 to 30 mm. The irradiation unit 150 includes, for example, a stage 151, a stage moving mechanism 152, and an aperture 153. The stage 151 is installed in the processing chamber 104 and holds the glass substrate 2. The stage moving mechanism 152 two-dimensionally moves the stage 151 in the Y-axis direction and the Z-axis direction in order to move the irradiation point of the gas cluster 129 on the glass substrate 2. By controlling the moving speed, the etching amount can be controlled and the glass substrate 2 can be flattened. The stage moving mechanism 152 can also move the stage 151 in the X-axis direction. Further, the stage moving mechanism 152 can rotate the stage 151 around a rotation axis extending in the Y-axis direction. The aperture 153 is provided in the middle of the passage of the gas cluster 129, and enhances the uniformity of the strength of the gas cluster 129. The gas cluster 129 passes through the opening of the aperture 153 and irradiates the glass substrate 2.

Next, the irradiation unit 150 of the processing apparatus 100 will be described with reference to FIGS. 7 to 9. In the present specification, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are the horizontal direction, and the Z-axis direction is the vertical direction. In the following description, the positive direction of the X-axis is the front and the negative direction of the X-axis is the rear. The irradiation direction of the gas cluster 129 indicated by the arrow in FIG. 7 is the positive direction on the X-axis.

As shown in FIG. 7, the irradiation unit 150 irradiates the beam-shaped gas cluster 129 forward, and the irradiated gas cluster 129 includes the first main surface 21, the end surface 23, the first chamfer surface 24, and the glass substrate 2. The notch surface 26 is locally etched. The first main surface 21 is arranged toward the rear and is arranged so as to be inclined diagonally upward. The inclination angle is not particularly limited, but is, for example, 5 °. By arranging the first main surface 21 so as to be inclined diagonally upward, it is possible to directly irradiate the lower end surface 23 of the four end surfaces 23 with the beam-shaped gas cluster 129. If the direction of the glass substrate 2 is reversed, it is naturally possible to locally etch the second main surface 22 and the second chamfered surface 25 of the glass substrate 2.

As shown in FIG. 9, the stage 151 is arranged to face the second main surface 22 of the glass substrate 2. The stage 151 is arranged in front of the glass substrate 2. The stage 151 may hold the glass substrate 2 via, for example, the spacer 155. The spacer 155 forms a gap between the stage 151 and the glass substrate 2. Compared with the case where the entire second main surface 22 of the glass substrate 2 comes into contact with the stage 151, it is possible to suppress the occurrence of contact scratches on the second main surface 22.

The spacer 155 may have a tapered tapered surface. If the second chamfered surface 25 of the glass substrate 2 is held by the tapered surface of the spacer 155, it does not come into contact with the second main surface 22 at all, so that the occurrence of contact scratches on the second main surface 22 can be reliably prevented. As shown in FIG. 8, a part of the spacer 155 is arranged outside the glass substrate 2 when viewed from the irradiation direction of the gas cluster 129.

In the present embodiment, a part of the spacer 155 is arranged outside the glass substrate 2 when viewed from the irradiation direction of the gas cluster 129, but the entire spacer 155 can be arranged inside the glass substrate 2. .. In that case, the spacer 155 contacts not the second chamfered surface 25 of the glass substrate 2 but the peripheral region excluding the quality assurance area of the second main surface 22.

Further, the stage 151 may hold the glass substrate 2 via the clamp 156. The glass substrate 2 can be stably held in a vacuum. The entire clamp 156 is arranged outside the glass substrate 2 when viewed from the irradiation direction of the gas cluster 129. The clamp 156 holds, for example, the end surface 23 of the glass substrate 2. A plurality of clamps 156 are provided at intervals along the peripheral edge of the glass substrate 2.

Although the clamp 156 presses the end surface 23 of the glass substrate 2 in the present embodiment, the clamp 156 may press the peripheral region 28 of the first main surface 21 of the glass substrate 2. Further, the clamp 156 may hold the first chamfered surface 24 of the glass substrate 2. Also in these cases, a part of the clamp 156 is arranged outside the glass substrate 2 when viewed from the irradiation direction of the gas cluster 129.

By the way, as shown in FIG. 1, the glass substrate 2 is subjected to a polishing step, an inspection step, a film forming step, and the like after the etching step of irradiating the gas cluster 129. These processes are collectively called a post-process. In the post-process, the end face 23 of the glass substrate 2 is pressed against a holder, a positioning tool, or the like. Therefore, the end face 23 is easily scratched.

Therefore, in the present embodiment, by irradiating the gas cluster 129, an element other than fluorine (F) and fluorine (hereinafter, also referred to as “A”) is driven into the end face 23 of the glass substrate 2, and the vicinity of the end face 23 is driven. Soften. Since the hardness in the vicinity of the end face 23 is soft, the vicinity of the end face 23 can be deformed so as to absorb the stress that extends the scratch. Therefore, the extension of the wound can be suppressed, and the decrease in the yield can be suppressed.

A is not particularly limited as long as it forms a gas cluster 129 together with F, and is, for example, carbon (C), boron (B), hydrogen (H), nitrogen (N), sulfur (S), and selenium (Se). ), Tellur (Te), or Tungsten (W). As will be described in detail later, A is preferably an element having a small number of valence electrons and preferably an element having a small atomic radius. Specifically, A is preferably carbon (C), boron (B), or nitrogen (N), and more preferably carbon (C).

As shown in FIG. 10, when the gas cluster 129 is driven into the glass substrate 2, the highly reactive fluorine breaks the Si—O bond near the glass surface. As a result, Si, O, F, and A are randomly bonded and the density becomes sparse, so that it is presumed that the hardness of the glass surface becomes soft.

If the density of the glass surface becomes sparse, compressive stress does not occur on the glass surface, so that the hardness of the glass surface does not become hard. For the purpose of reducing the density of the glass surface, A is preferably an element having a small number of valence electrons and preferably an element having a small atomic radius. As described above, A is preferably carbon, boron, or nitrogen, and more preferably carbon. The gas cluster 129 formed by A and F is preferably CF ₄ , CHF ₃ , CH ₂ F ₂ , BF ₃ , or NF ₃ , and more preferably CF ₄ , CHF ₃ , or CH ₂ F ₂ . .. CF _{4 and the} like are easier to handle than _{BF 3} and NF _3.

Further, if the density of the glass surface becomes sparse, compressive stress does not occur on the glass surface, so that the glass substrate 2 is not deformed due to the compressive stress. Therefore, the flatness of the first main surface 21 and the second main surface 22 of the glass substrate 2 is good.

F and A are driven into the end surface 23 of the glass substrate 2. In S103 of FIG. 1, the gas cluster 129 may be directly irradiated to the end surface 23 of the glass substrate 2, or the gas cluster 129 whose orientation is changed by collision with peripheral parts of the glass substrate 2 may be irradiated to the end surface of the glass substrate 2. You may type in 23. Further, in order to directly irradiate the four end faces 23 with the gas cluster 129, the glass substrate 2 may be rotated by 90 degrees about a rotation axis parallel to the X axis, and S103 may be performed a plurality of times. At this time, by controlling the irradiation time of the gas cluster 129 and the coordinates of the stage 151, it is possible to control the amounts of F and A driven into the four end faces 23. Examples of peripheral components of the glass substrate 2 include a stage 151, a spacer 155, a clamp 156, and the like.

The end face 23 includes F and A, and satisfies the following formula (1) and the following formula (2).

上記式（１）中、Ｄ１（ｘ）は、ＴＯＦ−ＳＩＭＳ（Ｔｉｍｅ−ｏｆ−Ｆｌｉｇｈｔ Ｓｅｃｏｎｄａｒｙ Ｉｏｎ Ｍａｓｓ Ｓｐｅｃｔｒｏｍｅｔｒｙ）で測定される、Ｓｉの強度で規格化したＦの強度であり、ｘは端面２３からの深さ（単位：ｎｍ）、ａ１ｘ+ｂ１はｘが２００以上４００以下の範囲におけるＤ１（ｘ）を最小二乗法で近似した直線である。上記式（２）中、Ｄ２（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＡの強度であり、ｘは端面２３からの深さ（単位：ｎｍ）、ａ２ｘ+ｂ２はｘが２００以上４００以下の範囲におけるＤ２（ｘ）を最小二乗法で近似した直線である。上記式（１）の左辺の値Ｓ１は、好ましくは１０以下である。また、上記式（２）の左辺の値Ｓ２は、好ましくは１以下である。

In the above formula (1), D1 (x) is the intensity of F standardized by the intensity of Si measured by TOF-SIMS (Time-of-Fright Section Ion Mass Spectrometry), and x is the intensity of F from the end face 23. Depth (unit: nm), a1x + b1 is a straight line that approximates D1 (x) in the range where x is 200 or more and 400 or less by the method of least squares. In the above formula (2), D2 (x) is the intensity of A normalized by the intensity of Si measured by TOF-SIMS, and x is the depth from the end face 23 (unit: nm), a2x +. b2 is a straight line obtained by approximating D2 (x) in the range where x is 200 or more and 400 or less by the least squares method. The value S1 on the left side of the above equation (1) is preferably 10 or less. Further, the value S2 on the left side of the above equation (2) is preferably 1 or less.

As described above, the end face 23 includes F and A and satisfies the above formulas (1) and (2). As a result, the hardness in the vicinity of the end face 23, which is applied to the holder, the positioning tool, or the like, can be softened. Since the hardness in the vicinity of the end face 23 is soft, the vicinity of the end face 23 can be deformed so as to absorb the stress that extends the scratch. Therefore, the extension of the wound can be suppressed, and the decrease in the yield can be suppressed.

In addition, instead of the end face 23, or in addition to the end face 23, the notch surface 26 may be pressed against the holder or the positioning tool. In this case, it is inevitable that the notch surface 26 will be scratched. However, if the scratches extend and large defects occur, the glass substrate is discarded as a defective product. Therefore, the yield is lowered.

Therefore, by irradiating the gas cluster 129, fluorine (F) and an element (A) other than fluorine may be driven into the notch surface 26 of the glass substrate 2 to soften the vicinity of the notch surface 26. Since the hardness in the vicinity of the notch surface 26 is soft, the vicinity of the notch surface 26 can be deformed so as to absorb the stress that extends the scratch. Therefore, the extension of the wound can be suppressed, and the decrease in the yield can be suppressed.

In S103 of FIG. 1, the gas cluster 129 may be directly irradiated on the notch surface 26 of the glass substrate 2, or the gas cluster 129 whose orientation is changed due to collision with peripheral parts of the glass substrate 2 is mounted on the glass substrate 2. It may be driven into the notch surface 26. Further, the glass substrate 2 may be rotated by 90 degrees about a rotation axis parallel to the X axis, and S103 may be performed a plurality of times. At this time, by controlling the irradiation time of the gas cluster 129 and the coordinates of the stage 151, it is possible to control the amount of F and A driven into all the notch surfaces 26. The notch surface 26 is easier to directly irradiate the gas cluster 129 than the end surface 23, and the contents of F and A can be increased.

The notch surface 26 irradiated with the gas cluster 129 includes F and A, and satisfies the following formulas (3) and (4).

上記式（３）中、Ｄ３（ｘ）は、ＴＯＦ−ＳＩＭＳ（Ｔｉｍｅ−ｏｆ−Ｆｌｉｇｈｔ Ｓｅｃｏｎｄａｒｙ Ｉｏｎ Ｍａｓｓ Ｓｐｅｃｔｒｏｍｅｔｒｙ）で測定される、Ｓｉの強度で規格化したＦの強度であり、ｘはノッチ面２６からの深さ（単位：ｎｍ）、ａ３ｘ+ｂ３はｘが２００以上４００以下の範囲におけるＤ３（ｘ）を最小二乗法で近似した直線である。上記式（４）中、Ｄ４（ｘ）は、ＴＯＦ−ＳＩＭＳで測定される、Ｓｉの強度で規格化したＡの強度であり、ｘはノッチ面２６からの深さ（単位：ｎｍ）、ａ４ｘ+ｂ４はｘが２００以上４００以下の範囲におけるＤ４（ｘ）を最小二乗法で近似した直線である。上記式（３）の左辺の値Ｓ３は、好ましくは１０以下である。また、上記式（４）の左辺の値Ｓ４は、好ましくは１以下である。

In the above formula (3), D3 (x) is the intensity of F standardized by the intensity of Si measured by TOF-SIMS (Time-of-Fright Section Ion Mass Spectrometry), and x is the notch surface 26. Depth from (unit: nm), a3x + b3 is a straight line that approximates D3 (x) in the range where x is 200 or more and 400 or less by the method of least squares. In the above formula (4), D4 (x) is the intensity of A normalized by the intensity of Si measured by TOF-SIMS, and x is the depth (unit: nm) from the notch surface 26, a4x. + b4 is a straight line obtained by approximating D4 (x) in the range where x is 200 or more and 400 or less by the least squares method. The value S3 on the left side of the above equation (3) is preferably 10 or less. Further, the value S4 on the left side of the above equation (4) is preferably 1 or less.

As described above, the notch surface 26 includes F and A and satisfies the above formula (3) and the above formula (4). As a result, the hardness in the vicinity of the notch surface 26, which is applied to the holder, the positioning tool, or the like, can be softened. Since the hardness in the vicinity of the notch surface 26 is soft, the vicinity of the notch surface 26 can be deformed so as to absorb the stress that extends the scratch. Therefore, the extension of the wound can be suppressed, and the decrease in the yield can be suppressed.

Next, the experimental data will be described mainly with reference to FIGS. 12 to 14. In Example 1, the gas cluster 129 was directly irradiated on the end face 23 of the glass substrate 2. Specifically, as shown in FIG. 11, the first main surface 21 is inclined backward and diagonally upward so that the beam 129A of the gas cluster 129 is obliquely incident on the lower end surface 23 of the glass substrate 2. And placed. The tilt angle was 5 °. As a result, the end face 23 of the glass substrate 2 was directly irradiated with the gas cluster 129. By rotating the glass substrate 2 by 90 degrees about a rotation axis parallel to the X axis, the four end faces 23 were directly irradiated with the gas cluster 129. As the raw material gas of the gas cluster 129, using CF ₄ gas. That is, the element (A) other than fluorine (F) was carbon (C). After irradiation with the gas cluster 129, the composition analysis of the end face 23 of the glass substrate 2 was measured by TOF-SIMS. The sample for composition analysis was cut out from the end face 23 of the glass substrate 2 and fixed to a jig so that the end face 23 faced upward and became substantially horizontal. For the composition analysis of the end face 23, TOF. SIMS5 was used. As the glass substrate 2, quartz glass containing _{TiO 2 was used.}

FIG. 12 shows the distribution of the F intensity / Si intensity in the depth direction obtained by measuring the end face 23 of the glass substrate 2 of Example 1 by TOF-SIMS. As is clear from FIG. 12, F was driven in the vicinity of the end surface 23 of the glass substrate 2. The value S1 on the left side of the above equation (1) was 1.00. When the composition analysis of the end face 23 was performed by TOF-SIMS before the irradiation of the gas cluster 129, S1 was 0.139.

Further, FIG. 13 shows the distribution of the C intensity / Si intensity in the depth direction obtained by measuring the end face 23 of the glass substrate 2 of Example 1 by TOF-SIMS. As is clear from FIG. 13, C was driven in the vicinity of the end surface 23 of the glass substrate 2. The value S2 on the left side of the above equation (2) was 0.07. When the composition analysis of the end face 23 was performed by TOF-SIMS before the irradiation of the gas cluster 129, S2 was 0.017.

FIG. 14 shows the hardness of the end face 23 of the glass substrate 2 of Example 1 before and after irradiation with gas clusters. The hardness was measured by an ultra-fine indentation hardness tester (trade name: ENT-1100a) manufactured by Elionix Inc. The pushing load was 60 mN, the holding time was 1000 ms, and the number of measurements was 100 times. In FIG. 14, H _min is the minimum value, H _25% is the 25th percentile, H _50% is the 50th percentile (median), H _75% is the 75th percentile, and H _max is the maximum value. Generally, when the measured values are arranged in ascending order, the value located at α% of the whole counted from the beginning is called the α percentile. As is clear from FIG. 14, it can be seen that the hardness of the gas cluster after irradiation is softer than that of the gas cluster before irradiation.

In Example 2, the gas cluster 129 was directly irradiated on the notch surface 26 of the same glass substrate 2 as in Example 1. As the raw material gas of the gas cluster 129, using CF ₄ gas. That is, the element (A) other than fluorine (F) was carbon (C). After irradiation with the gas cluster 129, the composition analysis of the notch surface 26 of the glass substrate 2 was measured by TOF-SIMS. The sample for composition analysis was cut out from the corner of the glass substrate 2 including the notch surface 26, and the notch surface 26 was horizontally fixed to the jig with the notch surface 26 facing upward. For composition analysis of the notch surface 26, TOF. SIMS5 was used.

FIG. 15 shows the distribution of the F intensity / Si intensity in the depth direction obtained by measuring the notch surface 26 of the glass substrate 2 of Example 2 by TOF-SIMS. As is clear from FIG. 15, F was driven in the vicinity of the notch surface 26 of the glass substrate 2. The value S3 on the left side of the above equation (3) was 4.83. When the composition analysis of the notch surface 26 was performed by TOF-SIMS before the irradiation of the gas cluster 129, S3 was 0.139.

Further, FIG. 16 shows the distribution of the C intensity / Si intensity in the depth direction obtained by measuring the notch surface 26 of the glass substrate 2 of Example 2 by TOF-SIMS. As is clear from FIG. 16, C was driven in the vicinity of the notch surface 26 of the glass substrate 2. The value S4 on the left side of the above equation (4) was 0.114. When the composition analysis of the notch surface 26 was performed by TOF-SIMS before the irradiation of the gas cluster 129, S4 was 0.017.

From the above results, it can be seen that the notch surface 26 of the glass substrate 2 of Example 2 was also softened by the irradiation of the gas cluster 129, similarly to the end surface 23 of the glass substrate 2 of Example 1.

The EUV glass substrate and its manufacturing method, the EUV mask blank, and the manufacturing method thereof have been described above, but the present disclosure is not limited to the above-described embodiment and the like. Various changes, modifications, replacements, additions, deletions, and combinations are possible within the scope of the claims. Of course, they also belong to the technical scope of the present disclosure.

1 EUV mask blank 2 Glass substrate 21 1st main surface 22 2nd main surface 23 End surface 24 1st chamfered surface 25 2nd chamfered surface 26 Notch surface 3 Reflective film 4 Absorbing film 129 Gas cluster 129A Beam

Claims (13)

A rectangular first main surface, a rectangular second main surface opposite to the first main surface, four end faces perpendicular to the first main surface and the second main surface, and the above. It has four first chamfered surfaces formed at the boundary between the first main surface and the end surface, and four second chamfered surfaces formed at the boundary between the second main surface and the end surface. ,
Formed of quartz glass containing TiO ₂
The end face contains fluorine (F) and an element (A) other than fluorine that forms a gas cluster together with fluorine, and satisfies the following formulas (1) and (2), a glass substrate for EUV.

In the above formula (1), D1 (x) is the intensity of F standardized by the intensity of Si measured by TOF-SIMS, and x is the depth from the end face (unit: nm), a1x +. b1 is a straight line obtained by approximating D1 (x) in the range of x of 200 or more and 400 or less by the least squares method, and in the above equation (2), D2 (x) is the intensity of Si measured by TOF-SIMS. It is the intensity of A standardized in, x is the depth from the end face (unit: nm), and a2x + b2 is a straight line that approximates D2 (x) in the range where x is 200 or more and 400 or less by the method of least squares. be. A rectangular first main surface, a rectangular second main surface opposite to the first main surface, four end faces perpendicular to the first main surface and the second main surface, and the above. Two adjacent first chamfered surfaces formed at the boundary between the first main surface and the end surface and four second chamfered surfaces formed at the boundary between the second main surface and the end surface. It has one end face and one or more notch surfaces formed obliquely to the first main surface so as to scrape off the corners of the first main surface.
Formed of quartz glass containing TiO ₂
The notch surface contains fluorine (F) and an element (A) other than fluorine that forms a gas cluster together with fluorine, and satisfies the following formulas (3) and (4), a glass substrate for EUV.

In the above formula (3), D3 (x) is the intensity of F standardized by the intensity of Si measured by TOF-SIMS, and x is the depth from the notch surface (unit: nm), a3x. + b3 is a straight line obtained by approximating D3 (x) in the range of x of 200 or more and 400 or less by the least squares method. It is the intensity of A standardized by the intensity, x is the depth from the notch surface (unit: nm), and a4x + b4 approximates D4 (x) in the range where x is 200 or more and 400 or less by the least squares method. It is a straight line. Claimed that the element (A) other than fluorine is carbon (C), boron (B), nitrogen (N), sulfur (S), selenium (Se), tellurium (Te), or tungsten (W). Item 2. The EUV glass substrate according to Item 1. The EUV glass substrate according to claim 3, wherein the element (A) other than fluorine is carbon (C). The EUV glass substrate according to any one of claims 1 to 4,
A reflective film that reflects EUV light, which is formed on the EUV glass substrate,
A mask blank for EUV having an absorbent film formed on the reflective film and absorbing the EUV light. The method for manufacturing a glass substrate for EUV according to claim 1.
A method for producing a glass substrate for EUV, which comprises irradiating the glass substrate for EUV with a gas cluster containing the fluorine and the element other than the fluorine, and driving the fluorine and the element other than the fluorine into the end face. The method for manufacturing a glass substrate for EUV according to claim 2.
A method for producing a glass substrate for EUV, which comprises irradiating the glass substrate for EUV with a gas cluster containing the fluorine and the element other than the fluorine, and driving the fluorine and the element other than the fluorine into the notch surface. 6. The gas cluster according to claim 6 or 7, _{wherein the gas cluster comprises CF 4} , CHF ₃ , CH ₂ F ₂ , C ₂ F ₆ , BF ₃ , NF ₃ , SF ₆ , SeF ₆ , TeF ₆ , or WF _6. A method for manufacturing a glass substrate for EUVL. The method for manufacturing a glass substrate for EUV according to claim 8, wherein the gas cluster comprises CF ₄ , CHF ₃ , or CH ₂ F _2. The EUV glass substrate according to claim 1, a reflective film for reflecting EUV light formed on the EUV glass substrate, and an absorbing film for absorbing EUV light formed on the reflective film. It is a method for manufacturing a mask blank for EUV having the above.
A method for producing a mask blank for EUV, which comprises irradiating the glass substrate for EUV with a gas cluster containing the fluorine and the element other than the fluorine, and driving the fluorine and the element other than the fluorine into the end face. The EUV glass substrate according to claim 2, a reflective film for reflecting EUV light formed on the EUV glass substrate, and an absorbing film for absorbing EUV light formed on the reflective film. It is a method for manufacturing a mask blank for EUV having the above.
A method for producing a mask blank for EUV, which comprises irradiating the glass substrate for EUV with a gas cluster containing the fluorine and the element other than the fluorine, and driving the fluorine and the element other than the fluorine into the notch surface. 13. The gas cluster according to claim 10 or 11, _{wherein the gas cluster comprises CF 4} , CHF ₃ , CH ₂ F ₂ , C ₂ F ₆ , BF ₃ , NF ₃ , SF ₆ , SeF ₆ , TeF ₆ , or WF _6. A method for manufacturing a mask blank for EUVL. The method for producing a mask blank for EUV according to claim 12, wherein the gas cluster comprises CF ₄ , CHF ₃ , or CH ₂ F _2.

Images