JP2017040900A - Production method of mask blank substrate, mask blank substrate, mask blank and photo mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a mask blank substrate capable of improving a flatness of an effective area of a main surface.SOLUTION: A production method of a mask blank substrate comprises a main surface polishing step of polishing a main surface of a substrate, the substrate comprises an almost rectangular main surface, an end surface which is almost vertical to the main surface, and an almost flat inclined surface for connecting the main surface and the end surface, before performing the main surface polishing step. The inclined surface is formed on at least one of four sides of the main surface and crosses the main surface with an obtuse angle. A polishing amount of the main surface in the main surface polishing step in a plate thickness direction is 50 μm or less. After performing the main surface polishing step, at least one inclined surface has an inclination angle which is larger than 45° and less than 90° to the main surface, and a width in a direction vertical to the end surface which is 0.1 mm or more, and 0.3 mm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a mask blank substrate, a mask blank substrate, a mask blank, and a photomask.

  The mask blank substrate manufacturing method includes a main surface polishing step of polishing the main surface of the substrate (see, for example, Patent Document 1). Patent Document 1 mentions the influence of the substrate mark on the flatness of the main surface. The substrate mark is formed in advance at the corner of the main surface before the main surface polishing step, and may deteriorate the flatness of the main surface during the main surface polishing step.

JP 2012-256038 A

  The mask blank substrate has a substantially rectangular main surface, an end surface substantially perpendicular to the main surface, and a substantially flat inclined surface connecting the main surface and the end surface. The inclined surfaces are formed on each of the four sides of the main surface and intersect at an obtuse angle with respect to the main surface. The inclined surface is formed in advance before the main surface polishing step, separately from the substrate mark. Chipping during main surface polishing can be suppressed.

  Patent Document 1 mentions the influence of the substrate mark on the flatness of the main surface, but does not mention the influence of the inclined surface. Since the influence of the inclined surface is not taken into consideration, the flatness of the effective area of the main surface may not be sufficient.

  Here, the effective area means an area corresponding to the opening pattern of the photomask, and means an area overlapping the opening pattern of the photomask in plan view. In the case of a 152 mm square substrate, for example, a 142 mm square area 5 mm or more inside from the end face of the substrate is an effective area.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a method for manufacturing a mask blank substrate that improves the flatness of the effective area of the main surface.

In order to solve the above problems, according to one aspect of the present invention,
A main surface polishing step for polishing the main surface of the substrate;
Prior to the main surface polishing step, the substrate has a substantially rectangular main surface, an end surface substantially perpendicular to the main surface, and a substantially flat inclined surface connecting the main surface and the end surface. The inclined surface is formed on at least one of the four sides of the main surface and intersects the obtuse angle with respect to the main surface;
The amount of polishing in the thickness direction of the main surface in the main surface polishing step is 50 μm or less,
After the main surface polishing step, at least one of the inclined surfaces has an inclination angle with respect to the main surface of greater than 45 ° and less than 90 ° and a width in a direction perpendicular to the end surface of 0.1 mm or more. A method for manufacturing a substrate for a mask blank that is 0.3 mm or less is provided.

  According to one aspect of the present invention, there is provided a method for manufacturing a mask blank substrate that improves the flatness of the effective area of the main surface.

It is a flowchart which shows the manufacturing method of the board | substrate by one Embodiment. It is a figure which shows the state of the board | substrate before and after the main surface grinding | polishing process by one Embodiment. It is a figure which shows the state of the board | substrate and polishing pad in the main surface grinding | polishing process by one Embodiment. It is a figure which shows the reflective mask blank by one Embodiment. It is a figure which shows the reflection type photomask by one Embodiment. It is a figure which shows the transmissive | pervious mask blank by one Embodiment. It is a figure which shows the transmission type photomask by one Embodiment. It is explanatory drawing of the measuring method of the inclination | tilt angle and width in an Example and a comparative example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

  FIG. 1 is a flowchart illustrating a substrate manufacturing method according to an embodiment. The substrate manufacturing method includes, for example, a chamfering step S11 and a main surface polishing step S12.

  The substrate provided for the chamfering step S11 is made of, for example, glass, and has two main surfaces and four end surfaces. The two main surfaces are parallel to each other. Each main surface is formed in a substantially rectangular shape. The four corners of each main surface may be chamfered or not chamfered. Each end face is substantially perpendicular to the two main surfaces, and the angle formed between the end face and the main surface is 88 ° or more and 92 ° or less.

  In addition, although the board | substrate provided to chamfering process S11 is formed with glass in this embodiment, you may form with a ceramic, a semiconductor, a metal, etc.

  In the chamfering step S11, an inclined surface that intersects the main surface at an obtuse angle is formed at the boundary between the main surface and the end surface of the substrate. The inclined surface is formed substantially flat. The inclined surface may be formed at both end portions in the plate thickness direction of each end surface, or may be formed only at one end portion in the plate thickness direction of each end surface. The inclined surface may be polished by a polishing pad, a polishing brush, a polishing tape or the like before the main surface polishing step S12 in order to remove a processing flaw during chamfering.

  In the main surface polishing step S12, the main surface of the substrate is polished. The number of main surfaces to be polished may be one or two. The two main surfaces may be polished at the same time or sequentially. When there are two main surfaces to be polished, it is preferable that inclined surfaces are formed in advance at both end portions in the plate thickness direction of each end surface. When there is one main surface to be polished, an inclined surface may be formed in advance only at one end in the thickness direction of each end surface. It is only necessary that an inclined surface that intersects an obtuse angle with respect to the main surface is formed in advance on the main surface side to be polished.

  In the main surface polishing step S12, the main surface of the substrate and the polishing surface of the polishing pad are relatively moved while being in contact with each other. The polishing surface of the polishing pad may be larger than the main surface of the substrate. The entire main surface of the substrate can be polished simultaneously. For example, the radius of the polishing surface of the polishing pad may be larger than the diameter of the carrier that holds the substrate. In this case, the carrier is rotated around the center line of the carrier while being revolved around the center line of the polishing pad.

  The polishing pad may be disposed on both sides in the plate thickness direction of the substrate, and two main surfaces of the substrate may be polished simultaneously. As the polishing pad, for example, a urethane polishing pad, a non-woven polishing pad, a suede polishing pad, or the like is used. These polishing pads have a soft polishing surface, for example, a polishing surface formed of a resin foam.

  A polishing slurry containing abrasive particles and a dispersion medium is supplied between the polishing pad and the substrate. As the abrasive, for example, colloidal silica or cerium oxide is used. As the dispersion medium, water, an organic solvent, or the like is used.

  In addition, although the manufacturing method of a board | substrate has chamfering process S11 in FIG. 1, it does not need to have chamfering process S11. Before the main surface polishing step S12, an inclined surface that intersects with the obtuse angle with respect to the main surface may be formed on the main surface side to be polished. For example, the inclined surface may be formed at the time of molding the molten glass into a plate shape.

  Moreover, the manufacturing method of a board | substrate may have processes other than chamfering process S11 and main surface grinding | polishing process S12, for example, may have a washing | cleaning process. In the cleaning process, the substrate is cleaned. The cleaning step is performed between the chamfering step S11 and the main surface polishing step S12, after the main surface polishing step S12, and the like.

  FIG. 2 is a diagram illustrating the state of the substrate before and after the main surface polishing step according to one embodiment. In FIG. 2, the two-dot chain line indicates the state of the substrate before the main surface polishing step, and the solid line indicates the state of the substrate after the main surface polishing step.

  As shown by a two-dot chain line in FIG. 2, before the main surface polishing step S <b> 12, the substrate 10 includes a substantially rectangular main surface 11, an end surface 12 substantially perpendicular to the main surface 11, and the main surface 11 and the end surface. 12 and a substantially flat inclined surface 13 that connects the two. The inclined surface 13 is formed on at least one of the four sides of the main surface 11 and intersects the main surface 11 at an obtuse angle. Chipping during main surface polishing can be suppressed. In FIG. 2, the inclined surfaces 13 are formed at both ends in the thickness direction of the end surface 12, but may be formed only at one end in the thickness direction of the end surface 12.

  Prior to the main surface polishing step S12, at least one inclined surface 13 has an inclination angle θ1 with respect to the main surface 11 greater than 45 ° and less than 90 °, and a width W1 in a direction perpendicular to the end surface 12 is zero. .1 mm or more and 0.35 mm or less. The inclination angle θ1 is 0 ° when the inclined surface 13 is parallel to the main surface 11, and 90 ° when the inclined surface 13 is parallel to the end surface 12. The average value in each inclined surface 13 is employ | adopted for width W1 and inclination | tilt angle (theta) 1. The width W1 and the inclination angle θ1 may be different values or the same value for each inclined surface 13.

  The polishing amount PA in the thickness direction of the main surface 11 in the main surface polishing step S12 is generally 50 μm or less. When the polishing amount PA is 50 μm or less, deterioration of the flatness of the main surface 11 due to the main surface polishing step S12 can be suppressed. The polishing amount PA is preferably 200 nm or more and 2000 nm or less. If the polishing amount PA is 200 nm or more, the processing marks on the main surface 11 can be sufficiently removed. If the polishing amount PA is 2000 nm or less, the width W1 of the inclined surface 13 hardly fluctuates by the main surface polishing step S12.

  As shown by a solid line in FIG. 2, after the main surface polishing step S <b> 12, at least one inclined surface 13 has an inclination angle θ <b> 2 with respect to the main surface 11 that is greater than 45 ° and smaller than 90 ° and The width W2 in the vertical direction is not less than 0.1 mm and not more than 0.3 mm. The inclination angle θ2 is 0 ° when the inclined surface 13 is parallel to the main surface 11, and 90 ° when the inclined surface 13 is parallel to the end surface 12. The inclination angle θ2 after the main surface polishing step S12 is substantially the same as the inclination angle θ1 before the main surface polishing step S12. The average value in each inclined surface 13 is employ | adopted for width W2 and inclination | tilt angle (theta) 2. The width W2 and the inclination angle θ2 may be different or the same for each inclined surface 13.

  FIG. 3 is a diagram illustrating a state of the substrate and the polishing pad during the main surface polishing step according to an embodiment. In FIG. 3, the arrow direction indicates the direction of movement of the substrate relative to the polishing pad. In FIG. 3, the substrate is moved with the polishing pad fixed, but either may be moved, or both may be moved.

  In the main surface polishing step S12, the main surface 11 of the substrate 10 and the polishing surface 21 of the polishing pad 20 are relatively moved while being in contact with each other. At this time, the polishing surface 21 of the polishing pad 20 is elastically deformed by being pushed by the main surface 11 of the substrate 10, and forms a convex portion 21 a that rises along the inclined surface 13 in the moving direction of the main surface 11. A recess 21 b corresponding to the protrusion 21 a is formed inside the main surface 11. The cross-sectional area of the convex part 21a is substantially equal to the cross-sectional area of the concave part 21b. Since the recess 21b does not come into contact with the main surface 11, it can cause uneven polishing of the main surface 11.

  The inventor has found the following (1) to (3) through experiments and the like. (1) If the setting conditions (for example, load, rotation speed, revolution speed, etc.) of the polishing apparatus are the same, even if the inclination angle θ of the inclined surface 13 is different, the cross-sectional area of the recess 21b is substantially the same. (2) When the cross-sectional area of the concave portion 21b is the same, the greater the inclination angle θ of the inclined surface 13, the greater the depth of the concave portion 21b, while the smaller the width of the concave portion 21b. (3) When the width of the recess 21 b is the same, the recess 21 b approaches the end surface 12 as the width W of the inclined surface 13 is smaller.

  According to this embodiment, after the main surface polishing step S12, at least one inclined surface 13 has an inclination angle θ2 larger than 45 ° and a width W2 of 0.3 mm or less. The polishing amount PA in the main surface polishing step S12 is generally 50 μm or less. Therefore, before the main surface polishing step S12, at least one inclined surface 13 has an inclination angle θ1 larger than 45 ° and a width W1 of 0.35 mm or less. Therefore, in the main surface polishing step S <b> 12, the width of the concave portion 21 b is sufficiently small and the concave portion 21 b is sufficiently close to the end surface 12 in the vicinity of at least one of the four sides of the main surface 11. The concave portions 21b can be collected on the outer peripheral portion of the main surface 11, and the flatness of the effective area of the main surface 11 can be improved. The effective area means an area corresponding to the opening pattern of the photomask, and means an area overlapping the opening pattern of the photomask in plan view. The effective area is set at the center of the main surface 11. In the case of a 152 mm square substrate, for example, a 142 mm square area 5 mm or more inside from the end face of the substrate is an effective area. After the main surface polishing step S12, the inclination angle θ2 of the at least one inclined surface 13 is preferably 50 ° or more, more preferably 55 ° or more. Further, after the main surface polishing step S12, the width W2 of the at least one inclined surface 13 is preferably 0.25 mm or less, more preferably 0.2 mm or less.

  Further, according to the present embodiment, after the main surface polishing step S12, the inclination angle θ2 of the at least one inclined surface 13 is smaller than 90 °. Therefore, before the main surface polishing step S12, the inclination angle θ1 of the at least one inclined surface 13 is smaller than 90 °. Therefore, chipping during main surface polishing can be suppressed. After the main surface polishing step S12, the inclination angle θ2 of the at least one inclined surface 13 is preferably 80 ° or less, more preferably 70 ° or less.

  Furthermore, according to the present embodiment, after the main surface polishing step S12, the width W2 of the at least one inclined surface 13 is 0.1 mm or more. Therefore, before the main surface polishing step S12, at least one inclined surface 13 has a width W1 of 0.1 mm or more. Therefore, the inclined surface 13 can be easily formed in terms of processing accuracy. After the main surface polishing step S12, the width W2 of the at least one inclined surface 13 is preferably 0.15 mm or more.

  FIG. 4 is a diagram illustrating a reflective mask blank according to an embodiment. The reflective mask blank includes the polished substrate 10, the reflective film 30, and the absorbing film 40 in this order, which are indicated by solid lines in FIG. 2.

  The substrate 10 supports the reflection film 30 and the absorption film 40. The substrate 10 may be transparent or opaque and is made of glass, metal, semiconductor, or the like. The substrate 10 is preferably formed of quartz glass or titanium-doped quartz glass having a small thermal expansion coefficient.

  The reflective film 30 reflects light such as EUV (Extreme Ultra Violet). The reflection film 30 may be a multilayer reflection film in which high refractive index layers and low refractive index layers are alternately stacked, for example. The high refractive index layer is made of, for example, silicon (Si), and the low refractive index layer is made of, for example, molybdenum (Mo).

  The absorption film 40 absorbs light. The absorption film 40 is formed of, for example, a single metal, alloy, nitride, oxide, oxynitride or the like containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd).

  The absorption film 40 is a film on which an opening pattern is formed. For example, a photolithography method and an etching method are used for forming the opening pattern, and a resist film used at that time may be included in the mask blank. By forming an opening pattern in the absorption film 40, a reflective photomask is obtained.

  FIG. 5 is a diagram illustrating a reflective photomask according to an embodiment. The reflection type photomask shown in FIG. 5 is obtained by forming an opening pattern 40a in the absorption film 40 of the reflection type mask blank shown in FIG. The obtained reflective photomask is mounted on, for example, an exposure device of an EUV light source.

The reflective mask blank and the reflective photomask may further include films other than the reflective film 30 and the absorption film 40. For example, a protective film (for example, Ru, Si, TiO _2, etc.) that protects the reflective film 30 from etching of the absorption film 40 may be formed between the reflective film 30 and the absorption film 40. Further, a low reflection film (for example, TaON or TaO) having low reflection characteristics with respect to the inspection light of the opening pattern 40a of the absorption film 40 may be formed on the side opposite to the reflection film 30 with respect to the absorption film 40. . Further, a conductive film (for example, CrN) may be formed on the side opposite to the reflective film 30 with respect to the substrate 10.

  According to this embodiment, since the flatness of the effective area of the main surface of the substrate 10 can be improved, the accuracy of the opening pattern of the reflective photomask can be improved.

  FIG. 6 is a diagram illustrating a transmissive mask blank according to an embodiment. The transmissive mask blank has a polished substrate 10 and a light shielding film 50 indicated by a solid line in FIG.

  The substrate 10 supports the light shielding film 50. The substrate 10 is transparent and is made of, for example, glass. The substrate 10 is preferably made of quartz glass having a low coefficient of thermal expansion and a high light transmittance.

  The light shielding film 50 shields light. The light shielding film 50 is made of, for example, chromium (Cr).

  The light shielding film 50 is a film on which an opening pattern is formed. For example, a photolithography method and an etching method are used for forming the opening pattern, and a resist film used at that time may be included in the mask blank. By forming an opening pattern in the light shielding film 50, a transmission type photomask is obtained.

  FIG. 7 is a diagram illustrating a transmissive photomask according to an embodiment. The transmissive photomask shown in FIG. 7 is obtained by forming an opening pattern 50a in the light shielding film 50 of the transmissive mask blank shown in FIG. The obtained transmissive photomask is mounted on an exposure machine that uses, for example, an ArF excimer laser, a KrF excimer laser, a mercury lamp, or the like as a light source.

  Note that the transmissive mask blank and the transmissive photomask may have a halftone phase shift film instead of the light shielding film 50. The phase shift film provides a phase difference to light transmitted through the photomask, thereby improving resolution by using interference between transmitted light.

  According to this embodiment, since the flatness of the effective area of the main surface of the substrate 10 can be improved, the accuracy of the opening pattern of the transmissive photomask can be improved.

  In Test Examples 1 to 5, under the same conditions, except that the inclination angle θ2 and the width W2 of the inclined surface after main surface polishing were changed by changing the inclination angle θ1 and the width W1 of the inclined surface before main surface polishing. Two main surfaces were polished at the same time, and the flatness of a predetermined area of the main surface after polishing was measured. Test Examples 1-2 are Examples, and Test Examples 3-5 are Comparative Examples.

  As the substrate, a glass substrate having a 152 mm square and a thickness of 6.4 mm was prepared. The prepared glass substrate had two main surfaces, four end surfaces, and eight inclined surfaces, and the eight inclined surfaces had substantially the same inclination angle θ1 and substantially the same width W1.

  The inclination angle θ1 and width W1 before main surface polishing were measured by the method shown in FIG. The inclination angle θ2 and the width W2 after the main surface polishing were also measured by the method shown in FIG.

  FIG. 8 is an explanatory diagram of a method for measuring the tilt angle and the width in Examples and Comparative Examples. In FIG. 8, the unevenness of the substrate surface is exaggerated. In this measurement method, first, the least square plane 12P of the center area CA centered on the center point CP in the thickness direction of the end face 12 was obtained. The thickness direction dimension of the center area CA may be an integer obtained by rounding off the decimal point of the value obtained by dividing the plate thickness (2 mm or more) by 2, and is 3 mm in this substrate. Next, a point on the inclined surface 13 where the distance L from the least square plane 12P is 0.05 mm is P1, a center point on the main surface 11 in a direction perpendicular to the least square plane 12P is P2, and a point from the point P1 The points on the substrate surface in the section up to P2 are expressed by xy coordinates, and the substrate surface is approximated by a model formula. As a model formula, the following formula (1) was used.

式（１）において、４つの係数ａ、ｂ、ｃ、ｄは、基板表面上の各点の実測値とモデル式との残差の二乗和が最小となるように決定した。

In the equation (1), the four coefficients a, b, c, and d are determined so that the sum of squares of the residuals between the actually measured values of the points on the substrate surface and the model equation is minimized.

  The inclination angle θ was calculated using the following formula (2).

一方、幅Ｗは、最小二乗平面１２Ｐから交点Ｐ３までの距離として求めた。交点Ｐ３は、モデル式に含まれる２つの直線の交点とした。

On the other hand, the width W was determined as the distance from the least square plane 12P to the intersection P3. The intersection P3 is an intersection of two straight lines included in the model formula.

  Bellatrix N7512 manufactured by Filwel Co., Ltd. was used as the polishing pad. This polishing pad was disposed on both sides of the substrate in the plate thickness direction, and two main surfaces of the substrate were polished simultaneously. The polishing amount PA of each main surface was 1 μm.

  During polishing, a polishing slurry containing 20% by mass of colloidal silica having an average primary particle size of less than 20 nm, nitric acid as a dispersion medium, and pH adjusted to 2.0 was supplied to the polishing surface of the polishing pad.

  The flatness of the main surface after polishing was represented by a so-called PV value. The PV value is a difference in height between the highest position from the reference plane and the lowest position from the reference plane, with a plane obtained by approximating the main surface by the least square method as a reference plane. The smaller the PV value, the better the flatness. The surface shape of the main surface after polishing was measured with a Fizeau laser interference flatness measuring device (G310S manufactured by Fuji Film (former Fujinon)).

  There are three types of flatness measurement areas: small area A, medium area B, and large area C. The small area A was a 142 mm square effective area 5 mm or more inside from the end face of the substrate. The middle area B was a 144 mm square area 4 mm or more inside from the end face of the substrate. The large area C was a 146 mm square area 3 mm or more inside from the end face of the substrate.

  Table 1 shows the results of Test Examples 1 to 5.

表１から明らかなように、主表面研磨工程の後に、傾斜角θ２が４５°よりも大きく９０°よりも小さく、且つ幅Ｗ２が０．１ｍｍ以上０．３ｍｍ以下であれば、有効エリアである小エリアＡのＰＶ値を十分に低減できることがわかる。また、小エリアＡのＰＶ値が中エリアＢのＰＶ値や大エリアＣのＰＶ値よりも小さいことから、研磨パッドの研磨面のうち研磨ムラの原因となりうる部分が小エリアＡの外側に寄せ集められたことがわかる。

As is apparent from Table 1, after the main surface polishing step, if the inclination angle θ2 is larger than 45 ° and smaller than 90 ° and the width W2 is 0.1 mm or more and 0.3 mm or less, it is an effective area. It can be seen that the PV value of the small area A can be sufficiently reduced. In addition, since the PV value of the small area A is smaller than the PV value of the middle area B and the PV value of the large area C, the portion of the polishing surface of the polishing pad that may cause polishing unevenness is brought outside the small area A. You can see that it was collected.

  As mentioned above, although embodiment of the manufacturing method of the board | substrate for mask blanks was demonstrated, this invention is not limited to the said embodiment etc., In the range of the summary of this invention described in the claim, various Modifications and improvements are possible.

DESCRIPTION OF SYMBOLS 10 Substrate 11 Main surface 12 End surface 13 Inclined surface 20 Polishing pad 21 Polishing surface 30 Reflective film 40 Absorbing film 40a Opening pattern 50 Shading film 50a Opening pattern

Claims (8)

A main surface polishing step for polishing the main surface of the substrate;
Prior to the main surface polishing step, the substrate has a substantially rectangular main surface, an end surface substantially perpendicular to the main surface, and a substantially flat inclined surface connecting the main surface and the end surface. The inclined surface is formed on at least one of the four sides of the main surface and intersects the obtuse angle with respect to the main surface;
The amount of polishing in the thickness direction of the main surface in the main surface polishing step is 50 μm or less,
After the main surface polishing step, at least one of the inclined surfaces has an inclination angle with respect to the main surface of greater than 45 ° and less than 90 ° and a width in a direction perpendicular to the end surface of 0.1 mm or more. The manufacturing method of the board | substrate for mask blanks which is 0.3 mm or less. A substantially rectangular main surface, an end surface substantially perpendicular to the main surface, and a substantially flat inclined surface connecting the main surface and the end surface, wherein the inclined surface is at least four sides of the main surface. Formed into one and intersects the main surface at an obtuse angle,
The at least one inclined surface has an inclination angle with respect to the main surface of greater than 45 ° and less than 90 °, and a width in a direction perpendicular to the end surface is not less than 0.1 mm and not more than 0.3 mm. Blank substrate. A substrate according to claim 2;
A mask blank having a film on which an opening pattern is formed.   The mask blank according to claim 3, wherein the film is a light shielding film that shields light. The film is an absorption film that absorbs light,
The mask blank according to claim 3, further comprising a reflective film that reflects the light between the absorption film and the substrate. A substrate according to claim 2;
A photomask having a film having an opening pattern.   The photomask according to claim 6, wherein the film is a light-shielding film that shields light. The film is an absorption film that absorbs light,
The photomask according to claim 6, further comprising a reflective film that reflects the light between the absorption film and the substrate.

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