JP2019197768A - Synthetic quartz glass substrate for imprint mold - Google Patents

Abstract

To provide formulation of shape necessary for an imprint mold and a synthetic quartz glass substrate for the imprint mold based on the formulation.SOLUTION: In a synthetic quartz glass substrate 1 for an imprint mold having a vertical length L1 and a horizontal length L2 (where L1≥L2), for a circular region 2 surrounded by a circle having a radius R (where L2-2R≥10 mm) from the substrate center O on the back surface facing the surface on which a mold pattern is formed, the coefficient of the fourth term when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is -(2R/100,000×1) μm or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a synthetic quartz glass substrate for imprint molds.

In imprint technology, which is one of the alternative technologies for photolithography that has become popular in recent years, various shapes of substrates are used for molds used for imprinting, and the front surface, back surface, end surface, and chamfered portion of the substrate are used. There are many cases of processing.
The imprint technology is a technique that presses a mold with a micrometer or nanometer-size concavo-convex pattern on the surface of the substrate in advance against the work material or resin formed on the surface, and transfers the fine pattern precisely at once. is there. In particular, as a UV nanoimprint mold, synthetic quartz glass is advantageous in terms of low thermal expansion, purity, heat resistance, and chemical resistance in IC applications that require fine patterns.

The imprint process has advantages such as cost reduction by shortening the process and high transfer reproducibility as compared with the conventional method. However, since the imprint process is performed by 1: 1 direct contact between the mold and the workpiece, there are various imprint processes. There are problems specific to imprinting that are not found in conventional photolithography, such as defects and the need for high shape accuracy of the entire mold.
In many cases, the concavo-convex engraving included in the manufacturing process of the imprint mold is often performed by a photolithography method and wet etching using a semiconductor manufacturing apparatus or an equivalent apparatus. The order of several hundred to several nanometers is required for the pattern position accuracy in semiconductor manufacturing, but not only the processing accuracy of a fine pattern but also a highly accurate shape is defined up to the front and back surfaces and end surfaces of the mold.

Originally, the flatness of both the front and back surfaces of a photomask has been regarded as important in IC applications. For example, in Patent Document 1, a high planarization technique for achieving a high flatness required for an exposed region of a photomask. There is a disclosure.
Patent Document 2 discloses the importance of the flatness of the substrate gripping region at the peripheral edge of the outer periphery.
On the other hand, in Patent Document 3, in a state-of-the-art reflective exposure method such as EUV lithography, the guaranteed area is defined as 300 nm or less for the flatness of the back surface.

JP 2002-318450 A JP 2005-043838 A JP 2012-505704 A

However, in a transmissive photomask substrate, the flatness of the surface on which a pattern is drawn is important, and the flatness of the back surface is not strictly defined as compared with the flatness of the surface. And the part important in the flatness of the back surface remains on the outer periphery of the substrate used for gripping. In this respect, Patent Document 1 also only describes the front surface and does not describe the back surface.
Moreover, in patent document 2, although the outer periphery holding | grip part of a surface is described more specifically, there is no reference to a back surface. This is because the back side of the substrate in photolithography is a non-contact part, and even if there is an influence on the pattern, it is considered that the influence on the pattern can be canceled sufficiently by the optical correction and illumination method in the exposure apparatus. is there.
Furthermore, in the reflective mask used for EUV lithography, the guaranteed area on the back surface is defined as being highly flat like the front surface, and Patent Document 3 describes that both the front and back surfaces need to be highly flat. The smaller the degree, the better. There is no requirement or description about the shape.

On the other hand, in the imprint mold, there is a process characteristic that the pattern is physically stamped and contacted to the transfer side, and then peeled off. And it is necessary to fix firmly. As the fixing method, adsorption or mechanical fixation is conceivable. In the case of adsorption, the necessity of contact between the adsorbing table etc. and the back surface can be determined by physically imprinting even in the case of mechanical fixation. There is often a need for contact with etc. At this time, members that come into contact with the back surface of the substrate and the stage are deformed due to the shape and stress at the time of imprinting, but the surface pattern surface is also deformed due to the deformation of the substrate. Due to this deformation, the pattern formed on the surface is also deformed, and the pattern is displaced in the plane direction. In particular, in the case of the back surface shape with low central symmetry, the pattern causes a non-linear shift, and in the case of the concave back surface, it is considered that the state of deformation changes every time it is adsorbed. The reproducibility becomes poor. In either case, it becomes difficult to make corrections or corrections in advance or afterwards.
In the formation of fine patterns including IC applications, the allowable value of pattern misalignment is particularly severe at a level of several nanometers, and the above problem can be a very serious problem in fine pattern transfer.

  This invention is made | formed in view of the said situation, and it aims at provision of the synthetic quartz glass substrate for imprint molds based on formulation of a shape required for an imprint mold based on this.

  As a result of intensive studies to achieve the above object, the present inventors have found a back surface shape of a synthetic quartz glass substrate suitable for imprint molding and completed the present invention.

That is, the present invention
1. A synthetic quartz glass substrate for imprint molding having a vertical length L1 and a horizontal length L2 (where L1 ≧ L2), and a radius R (from the substrate center on the back surface facing the surface on which the mold pattern is formed) However, for a circular region surrounded by a circle of L2-2R ≧ 10 mm), the coefficient of the fourth term when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is − (2R / 100,000 × 1) Synthetic quartz glass substrate for imprint mold, characterized by being not less than μm,
2. For the circular region, the coefficients of the fifth term to the eighth term when the approximate analysis is performed with the first term to the eighth term in the Zernike polynomial are − (2R / 100,000 × 1) μm to (2R / 100). , 1,000 × 1) μm synthetic quartz glass substrate for imprint mold,
3. For the circular region, the sum of the absolute values of the coefficients of the fifth to eighth terms when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is 4 × (2R / 100,000 × 1). 1 or 2 synthetic quartz glass substrate for imprint mold of μm or less,
4). The synthetic quartz glass substrate for imprint molds according to any one of 1 to 3, having a step processing region in which a step portion is formed in the circular region,
5. 4 of the synthetic quartz glass substrate for imprint mold, wherein the stepped portion is a non-through hole or a through hole;
6). For the region excluding the stepped region from the circular region, the coefficient of the fourth term when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is − (2R / 100,000 × 0.6). ) 4 or 5 synthetic quartz glass substrate for imprint molds of μm or more,
7. For the region excluding the stepped region from the circular region, the coefficient of the fifth term to the eighth term when the approximate analysis is performed with the first term to the eighth term in the Zernike polynomial is − (2R / 100,000). × 0.6) 4 or 5 synthetic quartz glass substrate for imprint molds of μm or more,
8). The sum of the absolute values of the coefficients in the fifth to eighth terms when the approximate analysis is performed in the first to eighth terms in the Zernike polynomial for the region excluding the stepped region from the circular region is 4 ×. (2R / 100,000 × 0.6) 4 or 5 synthetic quartz glass substrate for imprint mold of not more than μm,
9. In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) The synthetic quartz glass substrate for imprint molds of 4 or 5, wherein the coefficient of the fourth term when the approximate analysis is performed in the first term to the eighth term is − (2R / 100,000 × 0.5) μm or more ,
10. In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) When the approximate analysis is performed in the first term to the eighth term, the coefficients of the fifth term to the eighth term are-(2R / 100,000 × 0.2) to (2R / 100,000 × 0.2). 4 or 5 synthetic quartz glass substrate for imprint mold of μm,
11. In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) The sum of absolute values of the coefficients of the fifth term to the eighth term when approximate analysis is performed in the first term to the eighth term is 4 × (2R / 100,000 × 0.2) μm or less 4 or A synthetic quartz glass substrate for 5 imprint molds is provided.

  According to the synthetic quartz glass substrate for imprint mold of the present invention, the amount of deformation of the substrate at the time of imprinting can be reduced, and high reproducibility of the deformation behavior can be obtained, so the shape between the imprint mold pattern and the transfer pattern Reproducibility and process stability can be achieved.

It is a bird's-eye view which shows the back surface of the synthetic quartz glass substrate for imprint molds of this invention. It is a bird's-eye view of the back surface of the board | substrate in which the non-through hole and through-hole which are level | step-difference parts were formed. It is a figure which shows the ring-shaped area | region enclosed with the arbitrary circle | round | yen of radius R1 in the area | region which excluded the level | step difference process area | region from the circular area | region, and the circle | round | yen of radius R2.

Hereinafter, the present invention will be described in more detail.
The first synthetic quartz glass substrate for imprint mold according to the present invention has a vertical length of L1 and a horizontal length of L2 (where L1 ≧ L2), and faces the surface on which the mold pattern is formed. The coefficient of the fourth term when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial for a circular region surrounded by a circle with a radius R (where L2-2R ≧ 10 mm) from the substrate center on the back surface , − (2R / 100,000 × 1) μm or more.

  The relationship between the vertical length L1 and the horizontal length L2 is preferably L1 = L2 in order to obtain a more uniform deformed shape, but is particularly limited because there are many rectangular substrates such as a liquid crystal substrate. It is not something. L1 is preferably 30 to 3,000 mm, more preferably 100 to 2,000 mm, and L2 is preferably 100 to 1,500 mm, more preferably 120 to 1,400 mm.

In the present invention, Ultra Flat (manufactured by Corning Tropel) or the like is used for the analysis of the flatness of the back surface and the Zernike coefficient.
The Zernike polynomial is represented by the following mathematical formula, and the orders and contents of the first term to the eighth term are as shown in Table 1.

（式中、Ｂ_nmは、フリンジゼルニケ係数である。）

(In the formula, B _nm is a fringe Zernike coefficient.)

As a result of intensive studies on the number of terms required in the above Zernike polynomials, the present inventors have approximated the back surface shape as a polynomial up to the eighth term, so that the substrate deformation when the substrate back surface is absorbed and imprinted is imprinted. It has been found that suitable conditions for shape stabilization can be derived.
In the Zernike polynomial, the first term is a constant term, and the second and third terms are the X direction of the adsorption region on the back surface of the substrate (a circular region surrounded by a circle with a radius R from the center of the synthetic quartz glass substrate), respectively. , Shows the inclination of the surface in the Y direction. Since the imprint process itself must be parallel on the imprint mold side and the transferred side, the device performance, process accuracy, flatness of the transferred side substrate, etc. are complex factors. As a matter to be considered, the present invention does not consider the substrate shape.

The fourth term is a term indicating central symmetry and corresponds to the linear deformation of the substrate surface on which the pattern is formed, so that the substrate is deformed by applying external force to the pattern design before pattern formation or after pattern formation. This is an index for performing magnification correction. In magnification correction, there is an upper limit in the mechanism, correction at the time of pattern formation, and the like, so it is necessary to determine the magnitude of the absolute value.
The fourth term is a term that approximates a centrally symmetric shape, and the degree of unevenness is expressed by a coefficient. Therefore, in the back surface suction mechanism having this centrally symmetric shape, the coefficient of the fourth term and the deformation of the substrate are particularly important. Therefore, the correction of the magnification from the coefficient is easy before and after the pattern formation.
In general, the non-guaranteed area of the substrate in the IC is often within 5 mm from the end face, and in that area, the flatness is often poorer than the in-guaranteed area. Further, the outer peripheral portion may be installed or fixed on a work holder or the like of the apparatus, and stress is applied at the time of suction holding or stamping.
Therefore, the region contributing to the deformation of the pattern shape is, as shown in FIG. 1, a synthetic quartz glass substrate 1 having a vertical length L1 and a horizontal length L2, generally excluding the non-guaranteed region. Consider a circular region 2 surrounded by a circle with a radius R from the center O of the glass substrate 1.
In the present invention, as described above, the fourth term coefficient when this circular region 2 is subjected to the approximate analysis with the first to eighth terms in the Zernike polynomial is − (2R / 100,000 × 1) μm or more. However, it is preferably − (2R / 100,000 × 0.5) μm to 0 μm. By setting the fourth term coefficient within this range, the deformation of the pattern shape due to the adsorption of the substrate is only a parameter that can be corrected before and after the pattern formation, so that the pattern position accuracy is improved. For example, in the case of a 6-inch square synthetic quartz glass substrate, the fourth term is −1.42 μm or more, preferably −0.71 to 0 μm.

  Further, for example, as shown in FIG. 2, in the synthetic quartz glass substrate 1, when the step processing for forming the non-through hole 2A or the through hole 2B or the like as the step portion in the circular region 2 is performed, In the region excluding the stepped portion (the non-through hole 2A and the through hole 2B in FIG. 2) from the circular region 2, the fourth term coefficient when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is It is preferably − (2R / 100,000 × 0.6) μm or more, more preferably − (2R / 100,000 × 0.4) μm to 0 μm. By doing so, it is possible to provide a substrate in which the deformation amount of the substrate surface is stable and can be easily corrected. For example, in the case of a 6-inch square synthetic quartz glass substrate, the fourth term coefficient in the region excluding the stepped portion from the circular region is preferably −0.86 μm or more, more preferably −0.57 to 0 μm.

Further, in the case of substrate suction, suction starts from the central convex portion on the back surface, and suction proceeds toward the outer peripheral side. It is the slope on the inner side that greatly affects the amount of deformation at that time. For example, as shown in FIG. 3, in the synthetic quartz glass substrate 1, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a radius R2 concentric therewith (where R2−R1 = 10 mm) In the ring-shaped region 3 surrounded by the circle, it is preferable that the inclination in this region is more strictly defined.
Specifically, for the ring-shaped region 3, the fourth term coefficient when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is − (2R / 100,000 × 0.5) μm or more. It is preferable that it is − (2R / 100,000 × 0.5) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, the fourth term coefficient in the ring-shaped region is preferably −0.71 μm or more, more preferably −0.71 to 0 μm.

  The back flatness is preferably (2R / 100,000 × 2) μm or less in a circular region surrounded by a circle having a radius R (however, L2-2R ≧ 10 mm) from the viewpoint of the size of the coefficient of each term. More preferably, it is (2R / 100,000 × 1) μm or less.

Next, since the fifth to eighth terms are asymmetric components, they are terms that cause non-linear distortion and torsion at the time of adsorption and imprint imprinting, and all of them are preferably small values.
The fifth term to the eighth term are the terms of the center asymmetric component, and represent the asymmetric components excluding the concentric, highly symmetric shape of the fourth term. These components represent different shapes for each term, but even when viewed as a single component, asymmetrical deformation different from centrally symmetric equal deformation is induced, and deviation is generated from simple linear correction. Becomes difficult. Therefore, in actuality, it is considered that the combination of these components leads to complex distortion and local deformation that cannot be corrected by the imprint mold. Therefore, the fifth to eighth terms are preferably equal to or smaller than the absolute value of the fourth term, and the best shape is that the coefficient of each term is zero.

From this point of view, the coefficients of the fifth to eighth terms when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial for the circular region surrounded by the circle with the radius R from the center of the synthetic quartz glass substrate are It is preferably − (2R / 100,000 × 1) μm to (2R / 100,000 × 1) μm, and more preferably − (2R / 100,000 × 0.5) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, it is preferably −1.42 to 1.42 μm, more preferably −0.71 to 0 μm.
Furthermore, the total sum of the absolute values of the coefficients of the fifth to eighth terms is preferably 4 × (2R / 100,000 × 1) μm or less, more preferably 4 × (2R / 100,000 × 0. 5) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, it is preferably 5.68 μm or less, more preferably 2.84 to 0 μm.

Further, in the case where the above-described step machining is performed, the fifth term to the eighth term in the case where the approximate analysis is performed with the first term to the eighth term in the Zernike polynomial for the region excluding the step machining region from the circular region. The coefficient is preferably − (2R / 100,000 × 0.6) μm or more, and more preferably − (2R / 100,000 × 0.3) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, the thickness is preferably −0.86 μm or more, more preferably −0.43 to 0 μm.
Furthermore, the sum total of absolute values of the coefficients of the fifth term to the eighth term is preferably 4 × (2R / 100,000 × 0.6) μm or less, and more preferably 4 × (2R / 100,000 ×). 0.3) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, it is preferably 3.41 μm or less, more preferably 1.71 to 0 μm.

Similarly to the fourth term, a ring-shaped region surrounded by a circle having an arbitrary radius R1 and a concentric radius R2 (where R2−R1 = 10 mm) in the region excluding the stepped region from the circular region. The coefficients of the fifth term to the eighth term when the approximate analysis is performed on the first term to the eighth term in the Zernike polynomial are preferably − (2R / 100,000 × 0.2) to (2R / 100, 000 × 0.2) μm, more preferably − (2R / 100,000 × 0.1) to (2R / 100,000 × 0.1) μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, the thickness is preferably −0.28 to 0.28 μm, more preferably −0.14 to 0.14 μm.
Furthermore, the sum total of absolute values of the coefficients of the fifth term to the eighth term is preferably 4 × (2R / 100,000 × 0.2) μm or less, more preferably 4 × (2R / 100,000 ×). 0.1) μm to 0 μm. For example, in the case of a 6-inch square synthetic quartz glass substrate, the thickness is preferably 1.14 μm or less, more preferably 0.57 to 0 μm.

  Since the Zernike polynomial is only an approximation, a difference from the actual back surface shape of the synthetic quartz glass for imprint mold occurs when represented by the polynomials of the first to eighth terms. This difference, which is generally called “residual”, further includes higher-order asymmetric and symmetric components after the ninth term or the tenth term, so it should be limited so as not to exceed a certain level. is there.

The raw material substrate for imprint mold used in the present invention is not particularly limited. For example, synthetic quartz glass is molded into a desired shape, annealed, sliced into a desired thickness, and ground by grinding. After polishing the outer periphery as necessary, it is possible to use those obtained through rough polishing and precision polishing.
As the polishing step, either double-sided polishing or single-sided polishing may be used. However, double-sided polishing is generally preferable for finishing the thickness variation and flatness of the substrate with high accuracy. The polishing process includes a plurality of polishing processes called rough polishing and precision polishing, and the polishing agent, polishing pad and polishing rate used in each polishing process are appropriately changed to control surface roughness (Ra), surface defects, and shape. .

The surface roughness (Ra) of the raw material substrate is preferably 0.3 nm or less, more preferably 0.2 nm or less, from the viewpoint of the direct contact of the raw material substrate with the material to be transferred.
In addition, since imprints are transferred in direct contact with an object to be transferred, defects are also transferred at the same magnification. Therefore, when PSL standard particles are used, the entire surface of the raw material substrate detected with an inspection sensitivity of 150 nm is used. The number of defects is preferably 10 or less, more preferably 0.
Further, from the viewpoint of the stability of the deformed shape of the entire substrate due to back surface adsorption during imprinting, it is preferable that the back surface shape is a substantially convex shape with high central symmetry at the same time.

As the abrasive, silicon carbide, aluminum oxide, cerium oxide, zirconium oxide, manganese oxide, colloidal silica and the like are generally used, but it is preferable to use a colloidal silica-based abrasive in the final precision polishing step. The average particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 80 nm or less.
The polishing pad may be appropriately selected from conventionally used various polishing pads such as suede, non-woven fabric, and polyurethane foam. From the viewpoint of achieving both roughness and defect quality, the suede pad is the most suitable. preferable.

In order to make the back surface shape a substantially convex raw material substrate with high central symmetry, it is preferable to monitor and control the polishing shape in each step from rough polishing to precision polishing step. Specifically, since a polishing cloth having high hardness is used in the rough polishing process, the shape of the polishing surface plate is greatly affected. Since the shape of the front and back surfaces of the substrate is generated by a combination of unevenness, unevenness, unevenness, and unevenness depending on the shape of the upper and lower surface plates, the shape of the polishing surface plate is particularly important in the rough polishing step.
In the subsequent steps of precision polishing, a polishing cloth having a relatively low hardness is used in order to improve the surface roughness and defect quality as described above. Therefore, although it becomes difficult to be influenced by the polishing surface plate, since it is a polishing cloth with low hardness, the outer periphery of the substrate is often polished, so that the whole tends to be slightly convex. In any case, with the aim of improving the quality of the surface, such as surface roughness and surface defects, without reducing the flatness in the precision polishing process, the machining allowance by polishing becomes smaller and the shape change also decreases. .

From the above, in order to make the back surface shape into a substantially convex shape with high central symmetry, for example, the surface plate shape in the rough polishing step is a shape in which the upper surface plate is convex, and the lower surface plate is a shape that is nearly flat A slightly concave shape is preferable. By doing in this way, it becomes possible to make the back surface convex while the surface is flattened. Moreover, it is possible to make different shapes on the front and back sides by combining surface plate shapes having different irregularities and adjusting the polishing shape by inverting the substrate a plurality of times during the rough polishing step.
In consideration of the difference between the shape of the back surface at the end of the rough polishing process and the shape after performing precision polishing, the flatness of the entire back surface at the time of the rough polishing process is such that the back surface shape is suitable at the end of precision polishing. The shape is defined so as to be preferably 2 μm or less, more preferably 1.5 μm or less. If the final convex shape after rough polishing is too large, the negative value of the fourth term becomes large when the analysis by the Zernike polynomial is performed, so that the necessary correction amount in the subsequent precision polishing becomes large. This is because correction may be difficult or impossible.

In the above, the shape of the back surface of the imprint mold raw material substrate is mainly defined. However, since the imprint mold performs contact and transfer of the uneven shape formed on the surface, the surface flatness is uneven after transfer. Since it affects the shape accuracy, it is preferable that the flatness of the surface is also achieved at the same time as in the photomask for IC applications.
After cleaning the imprint mold raw material substrate thus manufactured, a metal such as Cr, Cu, Mo, Ni or the like or a metal oxide thereof is deposited on the imprint mold raw material substrate using a vapor deposition apparatus or a sputtering apparatus. A film and a metal nitride film are laminated by a conventional method. The film thickness to be laminated is preferably 200 nm or less, more preferably 10 to 50 nm.

Next, a photoresist is applied onto the metal film or metal oxide film. The photoresist may be either a positive type or a negative type, but a positive type resist is preferable in terms of accuracy and environment. Resist corresponding to electron beam, EUV, ArF, KrF, I-line, and g-line is selected according to the exposure wavelength. The thickness of the resist is preferably several nm to several tens of μm.
As the coating method, spin coating, spray coating, slit coating, or the like can be used, but spin coating is suitable for more uniform coating.

Subsequently, when an exposure machine is used, a photomask having a desired pattern and an alignment mark is set. When direct drawing is performed, desired pattern data is set. In the case of an exposure machine, an imprint mold substrate in which the above-described metal film or metal oxide film and a resist film are stacked is set in the exposure machine, and exposure is performed through a photomask pattern. In general, a photomask having a size larger than that of the imprint mold substrate is used to cover the entire area to be exposed. The dimensions of the photomask and the imprint mold substrate are not particularly limited, but it is preferable to select one of 5-7 inch square and 9 inch square defined in the SEMI standard. In the case of direct drawing, an electron beam or laser is used to aim only at the desired pattern shape on the substrate for imprint mold in which the above-mentioned metal film or metal oxide film and a resist film are laminated using an electron beam or laser light. A pattern is formed by direct irradiation.
After exposure with an exposure amount corresponding to the resist type and resist film thickness, the resist film is developed, rinsed with pure water, and dried.

Thereafter, the metal film, metal oxide film, or metal nitride film is etched by wet etching using a chromium etching solution, an acidic aqueous solution, an alkaline aqueous solution, or the like, or dry etching using a chlorine or fluorine-based gas. After obtaining the object pattern, the imprint mold substrate is etched based on the pattern to obtain a synthetic quartz glass substrate for imprint mold having a pattern shape portion having irregularities.
Etching of the imprint mold substrate is performed by soaking in an etching solution containing hydrofluoric acid or sodium fluoride to etch the imprint mold substrate, a so-called wet etching method, and using a fluorine-based gas that has been made plasma by applying a high frequency. There is a so-called dry etching method in which etching is performed. In any method, a structure in which the metal or metal oxide pattern portion has a convex shape is obtained by etching the glass while leaving the metal or metal oxide pattern portion.

Next, external processing is performed as an imprint mold substrate. Outline processing is a high-accuracy shape as a synthetic quartz glass substrate for imprint molds by processing any one or more of the front, back, end and chamfered portions of the synthetic quartz glass substrate for imprint molds into a desired shape. The purpose is to form.
At the time of the outer shape processing, it is necessary to protect the pattern forming part at the upper part of the step part of the synthetic quartz glass substrate for imprint mold having the step part. Examples of the protective film that protects the pattern forming portion include metals such as Cr, Cu, Mo, and Ni, oxide films or nitride films of these metals, and organic compound photoresist films.

Thereafter, the synthetic quartz glass substrate for imprint mold, the pattern forming portion of which is protected by the protective film, is fixed to the substrate processing base via the adhesive member.
Examples of the adhesive member include wax, epoxy adhesive, acrylic resin adhesive, UV curable resin, and the like. As the substrate processing base, ceramics, glass, or metal base is used.
After fixing the synthetic quartz glass substrate for imprint molds to the substrate processing pedestal, external processing is performed on the front surface, back surface, end surface, and chamfered portion including a part of the pattern forming surface.
As a member used for the outer shape processing, a rotary grindstone tool in which diamond, cubic boron nitride, or the like is fixed to the main shaft of an automatic processing machine such as a machining center programmed with a desired shape by electrodeposition or metal bond is used. The spindle speed of the rotary grindstone tool is not particularly limited, but is preferably 100 to 30,000 rpm, more preferably 1,000 to 15,000 rpm from the viewpoint of processing accuracy and productivity. Moreover, although there is no restriction | limiting also in a grinding speed, 1-10,000 mm / min is preferable from the surface of processing precision and productivity, and 10-1,000 mm / min is more preferable.

In order to cool or eliminate chips, it is preferable to carry out the processing with an emulsion, water-soluble, oil-based cutting fluid.
In outline processing, there are cases where the substrate size is changed, end surface processing for improving the flatness of the end surface, chamfered portion processing between the front and back surfaces and end surface or non-through or through hole processing are performed. It is possible to perform processing using a rotating grindstone tool and a cutting fluid.
Synthetic quartz glass substrates for imprint molds that have undergone external processing in this way are often non-mirror surfaces, so they are mirror-polished to improve the strength of the workpiece, improve cleanliness, reduce residual stress, etc. as necessary. I do.
As a mirror surface processing method, either or both of them are moved so that the imprint mold substrate and the rotary polishing pad swing relative to each other while the rotary polishing pad is brought into contact with the imprint mold substrate at a constant pressure. It is preferable to perform polishing. Although the rotary polishing pad may be impregnated with an abrasive, it is preferable to perform the processing in a state where a polishing abrasive slurry is interposed. The material of the polishing part of the rotary polishing pad is not limited as long as it can process and remove work pieces such as foamed polyurethane, cerium oxide impregnated polyurethane, zirconium oxide impregnated polyurethane, nonwoven fabric, suede, rubber, wool felt and the like. .

Examples of the abrasive grains when performing the polishing process with the abrasive grain slurry interposed are, for example, silica, ceria, alundum, white alundum (WA), FO, zirconia, SiC, diamond, titania, germania, etc. The particle size is preferably 10 nm to 10 μm, and these water slurries can be suitably used.
In addition, as a method of pressing the rotating polishing pad against the side surface of the substrate to be polished with a constant pressure, a method using a pressurizing mechanism such as a pneumatic piston or a load cell can be cited.

The substrate that has undergone the outer shape processing is cleaned as necessary. This cleaning can be performed using acidic aqueous solutions such as sulfuric acid, hydrofluoric acid, nitric acid, hydrochloric acid, oxalic acid and acetic acid, mixed acid aqueous solutions, alkaline aqueous solutions such as sodium hydroxide, potassium hydroxide and surfactants, xylene, acetone and alcohol. Use an organic solvent such as organic solvent as appropriate, and rinse with pure water.
The synthetic quartz glass substrate for imprint mold after cleaning is subjected to visual inspection and inspection by a defect inspection apparatus. For inspection of 150 nm class defects, an apparatus such as M1320, M3350, M6640, etc. (Lasertec) is used.
The flatness of the synthetic quartz glass substrate for imprint molds thus obtained is preferably 1 μm or less, more preferably 0 for the pattern formation region on the surface from the viewpoint of highly accurate shape transfer of the imprint pattern. .1 μm or less.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to the following Example.

[Example 1]
A 6-inch (152 mm) square synthetic quartz glass substrate is used as the imprint mold raw material substrate, and the flatness in the 142 mm square region on the back surface is 1.121 μm after lapping, polishing, and cleaning steps on the front and back surfaces of the substrate. Substrate was obtained.
When the shape of the back surface of the substrate was measured with Ultra Flat (manufactured by Corning Tropel) and Zernike analysis was performed in a circle region surrounded by a circle having a radius of 60 mm from the center of the synthetic quartz glass substrate, the coefficient of the fourth term was − The coefficient of 0.344 μm, the fifth to eighth terms was 0.004 to 0.042 μm, and the sum of absolute values was 0.073 μm, and a substrate having a very suitable back surface shape could be obtained.

[Example 2]
Using the same raw material substrate as in Example 1, a chromium film and a photoresist were formed on the surface, and exposure and development were performed using a photomask to form a 33 × 41 mm rectangular region pattern in the center of the substrate.
Next, wet etching processing was performed on the non-pattern forming region using a hydrofluoric acid aqueous solution containing ammonium fluoride to form a rectangular pattern with a height of 30 μm.
After etching, step processing is performed on a circular region surrounded by a circle with a radius of 32 mm from the center of the back surface of the synthetic quartz glass substrate, and isopropyl alcohol, hot concentrated sulfuric acid, a surfactant (PC302C, manufactured by Kao Corporation) and pure water are used. After cleaning, the shape of the back surface of the substrate was measured with an Ultra Flat (manufactured by Corning Tropel).
As a result of the measurement, a substrate having a flatness of 1.041 μm in the 142 mm square area on the back surface was obtained. Further, when a Zernike analysis was performed in a circular region surrounded by a circle with a radius of 60 mm excluding the stepped region from the circular region on the back surface, the coefficient of the fourth term was −0.318 μm, and the fifth to eighth terms The coefficient of -0.011 to 0.034 μm and the sum of absolute values was 0.079 μm, and a substrate having a very suitable back surface shape could be obtained.

[Example 3]
A substrate similar to that in Example 1 in which a 26 × 33 mm rectangular region pattern was formed on the substrate surface was wet-etched in a non-pattern forming region using an aqueous hydrofluoric acid solution containing ammonium fluoride, and the height of 30 μm was increased. A rectangular pattern was formed.
After etching, step processing is performed on a circular region surrounded by a circle with a radius of 32 mm from the center of the back surface of the synthetic quartz glass substrate, and isopropyl alcohol, hot concentrated sulfuric acid, a surfactant (PC302C, manufactured by Kao Corporation) and pure water are used. After cleaning, the shape of the back surface of the substrate was measured with an Ultra Flat (manufactured by Corning Tropel).
As a result of the measurement, a substrate having a flatness in the 142 mm square area of the back surface of 0.599 μm was obtained. Further, when an approximate analysis was performed on the first to eighth terms in the Zernike polynomial for a ring-shaped region surrounded by a circle with a radius of 35 mm and a circle with a radius of 45 mm excluding the stepped region from the circular region on the back surface, The coefficient of the fourth term was −0.282 μm, the coefficients of the fifth to eighth terms were −0.013 to 0.034 μm, and the total absolute value was 0.057 μm.
Further, when the ring-shaped region was shifted outward by 5 mm and the sum of the coefficient of the fourth term and the coefficients of the fifth term to the eighth term and the absolute value was measured, the results shown in Table 2 were obtained.

The fourth term coefficient is sufficiently small as 0.282 as an absolute value, the fifth term to the eighth term are -0.028 to 0.034, and the sum of absolute values is 0.057 to 0.084, A suitable substrate was obtained.
The fourth term coefficient of the ring-shaped region 35-45 has a larger absolute value than the fourth term coefficient of the ring-shaped region 60-70, and the region close to the center in the region where the stepped region is excluded from the circular region. It can be seen that the slope is large.

1 Synthetic quartz glass substrate for imprint mold 2 Circular region 2A Non-through hole 2B Through hole 3 Ring-shaped region L1 Vertical length of synthetic quartz glass substrate for imprint mold L2 Horizontal length of synthetic quartz glass substrate for imprint mold O substrate center R radius R1 radius R2 of an arbitrary circle in a region excluding the step machining region from the circular region radius of a circle concentric with the circle of radius R1 (R2−R1 = 10 mm)

Claims (11)

A synthetic quartz glass substrate for imprint mold having a vertical length L1 and a horizontal length L2 (where L1 ≧ L2),
Approximate analysis is performed on the first to eighth terms in the Zernike polynomial for a circular region surrounded by a circle with a radius R (where L2-2R ≧ 10 mm) from the center of the substrate on the back surface opposite to the surface on which the mold pattern is formed. A synthetic quartz glass substrate for imprint molds, wherein the coefficient of the fourth term in this case is − (2R / 100,000 × 1) μm or more.   For the circular region, the coefficients of the fifth term to the eighth term when the approximate analysis is performed with the first term to the eighth term in the Zernike polynomial are − (2R / 100,000 × 1) μm to (2R / 100). 2. The synthetic quartz glass substrate for imprint molds according to claim 1, wherein the synthetic quartz glass substrate is 1,000,000 × 1) μm.   For the circular region, the sum of the absolute values of the coefficients of the fifth to eighth terms when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is 4 × (2R / 100,000 × 1). The synthetic quartz glass substrate for imprint molds according to claim 1 or 2, which is not more than µm.   The synthetic quartz glass substrate for imprint molds according to any one of claims 1 to 3, further comprising a step processing region in which a step portion is formed in the circular region.   The synthetic quartz glass substrate for imprint molds according to claim 4, wherein the step portion is a non-through hole or a through hole.   For the region excluding the stepped region from the circular region, the coefficient of the fourth term when the approximate analysis is performed with the first to eighth terms in the Zernike polynomial is − (2R / 100,000 × 0.6). 6. The synthetic quartz glass substrate for imprint molds according to claim 4 or 5, wherein the synthetic quartz glass substrate has a thickness of μm or more.   For the region excluding the stepped region from the circular region, the coefficient of the fifth term to the eighth term when the approximate analysis is performed with the first term to the eighth term in the Zernike polynomial is − (2R / 100,000). The synthetic quartz glass substrate for imprint molds according to claim 4 or 5, wherein x is 0.6) m or more.   The sum of the absolute values of the coefficients in the fifth to eighth terms when the approximate analysis is performed in the first to eighth terms in the Zernike polynomial for the region excluding the stepped region from the circular region is 4 ×. The synthetic quartz glass substrate for imprint molds according to claim 4 or 5, which is (2R / 100,000 × 0.6) μm or less.   In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) 6. The imprint mold composition according to claim 4, wherein the coefficient of the fourth term when the approximate analysis is performed in the first to eighth terms is − (2R / 100,000 × 0.5) μm or more. Quartz glass substrate.   In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) When the approximate analysis is performed in the first term to the eighth term, the coefficients of the fifth term to the eighth term are-(2R / 100,000 × 0.2) to (2R / 100,000 × 0.2). The synthetic quartz glass substrate for imprint molds according to claim 4 or 5, which is μm.   In a Zernike polynomial, an arbitrary circle having a radius R1 in a region excluding the stepped region from the circular region and a ring-shaped region concentrically surrounded by a circle having a radius R2 (where R2−R1 = 10 mm) The sum of the absolute values of the coefficients of the fifth to eighth terms when the approximate analysis is performed in the first to eighth terms is 4 × (2R / 100,000 × 0.2) μm or less. The synthetic quartz glass substrate for imprint molds according to 4 or 5.

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