JP2017084837A - Reflection type photomask blank, method of manufacturing the same, and reflection type photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve positional accuracy of a transferred image by reducing the positional deviation amount of a transfer pattern, which causes a problem when forming a light shielding frame by reducing a reflective multilayer film around a pattern region and is resulting from compression stress of the reflective multilayer film, in manufacture of a reflection type photomask.SOLUTION: In this reflection type photomask blank, a reflective multilayer film 20, an absorption film 30 on top thereof, and a resist film 40 are laminated on one side of a substrate, and a back conductive layer is provided on the other side thereof. A fiducial mark 42, and a mark 34 for measuring a positional relation between itself and the fiducial mark are provided in the periphery of the reflection photomask plank, a reflective multilayer removal mark 35 from which the absorption film and the reflective multilayer film are removed is provided in the vicinity of the mark 34 for measuring the positional relation between itself and the fiducial mark, and the mark 34 for measuring the positional relation between itself and the fiducial mark is utilized to correct positional deviation due to stress release which is caused when forming a light shielding frame.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photomask blank used when a semiconductor device or the like is manufactured by a lithography technique, and relates to a reflective photomask blank, a photomask, and a manufacturing method used when exposure light is extreme ultraviolet light.

  Semiconductor integrated circuits are being miniaturized and highly integrated in order to improve performance and productivity, and as for lithography technology for forming circuit patterns, technological development for forming finer patterns with higher accuracy is being carried out. It is being advanced.

  With the development of these technologies, the light source of an exposure apparatus used for pattern formation is also shortened, and extreme ultraviolet light of 13.5 nanometers (Extreme Ultra Violet light, hereinafter referred to as “EUV light”). An apparatus and a pattern transfer process using the sapphire have been developed.

  At the wavelength of EUV light, the refractive index of all substances is close to 1, and the absorption is large. Therefore, a transmission type optical system cannot be used as in the case of using 193 nm ultraviolet light which has been conventionally used. Therefore, a reflection optical system using a reflection film in which a plurality of layers are laminated so that reflection at an interface is strengthened using a plurality of materials having different refractive indexes.

  A multilayer reflective film is also used for a photomask on which a transfer pattern such as a device circuit is formed. (Hereinafter, a reflective mask used for exposure using EUV light is referred to as an EUV mask.) As a method of forming a pattern, a method of patterning the reflective multilayer film itself and an absorption pattern on the reflective multilayer film are formed. However, the latter method is more advantageous and general in terms of forming a fine pattern with high accuracy.

  FIG. 9 illustrates a cross section of a general reflective photomask blank 100. The reflective photomask blank 100 includes a reflective multilayer film 20 that reflects EUV light on a substrate 10, an absorption film 30 that forms a pattern, a resist film 40 for selectively processing the absorption film, and the above-described layers. A conductive film 50 for using an electrostatic chuck is formed on the rear substrate surface to be formed.

  As for the positional accuracy of the pattern formed on the mask, very precise control is required in the reflection type photomask as well as the conventional photomask. Unlike a conventional photomask, an EUV mask, which is a reflective photomask, has an optical axis of exposure light that is incident on the reflective photomask substrate at a slight angle rather than perpendicularly. This angle is typically about 6 °. For this reason, the flatness of the substrate is also considered as a major factor affecting the position accuracy.

  For this reason, technical development is progressing to improve the flatness of both the EUV mask substrate and the electrostatic chuck used for adsorption in the exposure apparatus.

  On the other hand, since the incident direction of exposure light is slightly oblique as described above, there are various types of light reflected from the reflective photomask, such as different transfer characteristics between a pattern parallel to the exposure optical axis and a pattern perpendicular to the exposure optical axis. Asymmetry occurs. In order to reduce such an influence, it is obvious that the thinner the absorption pattern, the more advantageous.

  However, since the contrast of the reflected image is reduced when the absorption pattern is made thinner, the phase of the minute light reflected from the absorption pattern portion is reflected from the reflective multilayer film, as in the halftone phase shift mask in the conventional photomask. It has been devised to design so as to be shifted by about 180 ° with respect to the light (Patent Document 1).

  In addition, a proposal has been made to make the absorption film thin and provide a low-reflectance region so as to surround the circuit pattern so that light adjacent to the exposure block transferred thereby does not leak, which is called a light shielding frame. (Patent Document 2).

  Various methods for forming the light shielding frame are also disclosed in Patent Document 2, but the method of removing the reflective multilayer film by etching is the most effective.

  The multilayer reflective film is generally formed by alternately stacking 40 to 50 pairs of molybdenum and silicon with a thickness of about 4 nm and 3 nm, respectively. It is very difficult to produce such a reflective multilayer film without defects, and it is practically impossible to flatly correct a portion that is not flatly stacked on a defective portion on a substrate.

  In this way, it is extremely difficult to prepare a complete reflection type photomask blank having no defect in the reflective multilayer film, and if there are some defects, the pattern formation position is shifted so as to avoid it, and the defective part is overlapped with the absorption part. In other words, a technique has been developed in which a defect in the reflective multilayer film is corrected by correcting the absorption pattern so that normal transfer can be performed.

  As described above, a reference pattern is necessary to arrange so as to avoid the defect, and before forming the absorption film, a pattern called a fiducial mark is required before inspecting the defect of the reflective multilayer film. It is formed in advance and the position of the reflective multilayer film defect is recorded as a relative position with respect to the fiducial mark.

  As described above, in the EUV mask, a very flat substrate is used in order to increase the pattern position accuracy. However, although the reflective multilayer film is formed by ion beam sputtering, as shown in Patent Document 3, for example, the reflective multilayer film generally has internal stress in the compression direction, and the substrate is warped so that the reflective multilayer film side is convex. However, as a countermeasure against this, a technique of canceling stress with a conductive film formed on the back surface is disclosed (Patent Document 3).

  For example, the stress of the reflective multilayer film is a compressive stress of 400 MPa, and in this case, it is described that a commonly used substrate having a thickness of 6.35 mm warps about 0.6 microns (Non-Patent Document). 1).

  On the other hand, when the reflective multilayer film is removed by etching as a light shielding band around the pattern area as shown in the above-mentioned patent document, the stress of the reflective multilayer film is released at the end of the light shielding frame, thereby causing a positional shift. FIG. 10 roughly explains this phenomenon.

  FIG. 10A shows a cross-sectional view of the reflective multilayer film 20 formed on the EUV mask substrate. The portion where the light-shielding frame is formed by removing the reflective multilayer film around the pattern region is the stress of the reflective multilayer film. Can be ignored as shown in FIG. However, when the compressive stress of the reflective multilayer film is large, the internal stress is released at the end of the light shielding frame, so that the state shown in FIG. The figure exaggerates the deformations so that the phenomenon can be easily understood, and the complicated deformations are simplified.

In such a modification, it can be easily assumed that the amount of positional deviation increases as the distance from the end of the light shielding frame becomes closer. For this reason, the pattern within the light shielding frame and close to the edge of the light shielding frame is shifted from the design value toward the outside from the center of the substrate.

  Such a shift causes a malfunction due to an overlay error of each layer when a semiconductor device composed of a plurality of layers is sequentially manufactured in a lithography process.

  Even if it is not a direct device pattern, for example, if a chip alignment mark is arranged, even if alignment adjustment is performed by an exposure apparatus, it will be transferred with a slightly reduced size than the design and transferred onto the wafer. This is a factor that degrades the positional accuracy of the image.

  In the actual exposure process, the reflective photomask is attracted to a flat electrostatic chuck, but the above displacement is due to local stress relief at the edge of the light-shielding frame, and the back surface is flattened. Even if this is done, the amount of displacement in the film surface direction is not reduced.

JP 2004-207593 A Japanese Patent No. 4602430 JP 2002-299228 A

Proceedings of SPIE, Volume 6533, 653314 (2007)

  The present invention reduces the amount of misalignment of the transfer pattern due to the compressive stress of the reflective multilayer film, which becomes a problem when the reflective multilayer film around the pattern area is removed to form a light shielding frame in the production of a reflective photomask. It is another object of the present invention to provide a reflective photomask blank that can improve the positional accuracy of a transferred image.

  The present invention also provides a reflective photomask blank that is effective for correction in a direction perpendicular to the light shielding frame and that can sufficiently obtain a correction value near the corner of the light shielding frame.

  Furthermore, the difference in the deformation state of the substrate when measuring the position of the pattern of the reflective photomask and when the reflective photomask is mounted on the exposure apparatus is taken into consideration.

As a means for solving the above-mentioned problems, the invention according to claim 1 is a reflection type photo in which a reflective multilayer film is provided on one surface of a substrate, an absorption film is provided on the reflective film, and a back conductive layer is provided on the other surface. A mask blank,
A mark for measuring the positional relationship between the fiducial mark and the fiducial mark is provided on the outer periphery of the reflective photomask blank, and the mark for measuring the positional relationship with the previous fiducial mark. A region where the absorption film and the reflective multilayer film are partially removed is provided in the vicinity, and the shape obtained by partially removing the absorption film and the reflective multilayer film has a convex shape of 90 degrees inside. A reflective photomask blank.

A reflective photomask blank according to claim 2 is the reflective photomask blank according to claim 1, wherein a resist is coated on the absorption layer.

  The invention described in claim 3 is the reflective photomask blank according to claim 1 or 2, wherein the film is formed before and after the region where the absorbing film and the reflective multilayer film are partially removed is provided. This is a reflective photomask blank to which mark difference information for measuring the positional relationship with the dual mark is added.

  The invention according to claim 4 is a method for manufacturing a reflective photomask using the photomask blank according to claim 3, wherein stress is released when a light shielding frame is formed based on the difference information. When correcting the influence of the cause, the difference between the substrate state when measuring the position accuracy of the photomask pattern without being attracted to the electrostatic chuck and when attracted to the electrostatic chuck in the exposure apparatus is taken into consideration It is a manufacturing method of the reflection type photomask characterized by including a procedure.

  According to a fifth aspect of the present invention, there is provided a reflective photomask manufactured based on the reflective photomask manufacturing method according to the fourth aspect.

  The compressive stress of the reflective multilayer film for each reflective photomask blank can be quantified as the amount of misregistration of the transfer pattern, and the numerical value can be used to optimally correct the pattern and transfer it. It is possible to provide a reflective photomask that can accurately position the image.

It is the cross-sectional conceptual diagram which showed the reflective photomask blank which can convert data into the compressive stress of the reflective multilayer film of this invention. It is the conceptual diagram which looked at a part of reflective type photomask blank of the form of an example of implementation of this invention from the upper surface. It is a conceptual sectional view showing a reflective photomask of the present invention. It is explanatory drawing of the light shielding frame formed on the coordinate axis showing the position on a reflection type photomask substrate, and a reflection type photomask. It is explanatory drawing of the result of having calculated the deviation | shift amount of the X-axis direction by the stress of a reflective multilayer film. It is explanatory drawing of the result of having calculated the difference of the deviation | shift amount of the X-axis direction by the presence or absence of a light-shielding frame. It is explanatory drawing of the result calculated only within the inner edge part vicinity of the light-shielding frame among the calculation results of FIG. It is explanatory drawing which shows an example of embodiment of this invention. It is explanatory drawing showing the cross-section of the general reflection type photomask blank. It is explanatory drawing of the deformation | transformation by stress when a part of reflective multilayer film is removed and the light shielding frame is formed. It is explanatory drawing of the result of having calculated the difference in the deviation | shift amount of the X-axis direction by the holding | maintenance state of a reflective multilayer film.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 shows a reflective photomask blank 502 of the present invention, which selectively processes a reflective multilayer film 20 that reflects EUV light on a substrate 10, an absorption film 30 that forms a pattern, and an absorption film. The resist film 40 is laminated, a conductive film 50 for using an electrostatic chuck is formed on the back substrate surface, and a fiducial mark 42 and the fiducial mark are formed on the outer periphery of the reflective photomask blank. A position measurement mark 34 for measuring the positional relationship between the reflection multilayer film 20 and the absorption film 30 is partially formed in the vicinity thereof, and a reflection multilayer film removal mark 35 for misalignment inspection is partially formed. A reflective photomask blank 501 obtained by measuring the amount of positional deviation before and after forming the film removal mark 35 and obtaining information on positional deviation due to the formation of the light shielding frame (see FIG. 8 (o)). To become.
Further, a resist 40 is laminated on the reflective photomask blank 501 to form a reflective photomask blank 502 (see FIGS. 1 and 8 (p)).

  2 shows a position measurement mark 34 for measuring the positional relationship with the fiducial mark in FIG. 1 and a reflection multilayer film removal for misregistration inspection in which the multilayer film 20 and the absorption film 30 are partially removed in the vicinity thereof. It is the conceptual diagram seen from the upper surface about the part of the mark 35. FIG. For ease of explanation, the resist film 40 is omitted in FIG.

  In FIG. 2, the optimum size of the position measurement mark 34 is very small compared to the reflective multilayer film removal mark 35, but is drawn large for explanation. In addition, the arrangement and shape of the position measurement marks are merely examples, and do not limit the application conditions of the present invention.

  Further, in FIG. 2, the reflective multilayer film removal mark 35 has at least one 90 ° convex portion 350 inside. The 90 ° convex portion may be on the outer side of the reflective multilayer film removal mark 35 as shown in FIG. 2A, or the reflective multilayer film removal mark as shown in FIG. It may be arranged inside 35 and not in contact with the outer side.

  In FIG. 2A, a linear pattern having a width is bent by 90 ° to form a mark equivalent to the vicinity of the corner portion inside the light shielding frame as a reflective multilayer film removal mark. In FIG. 2B, a rectangular pattern having a smaller position measurement mark is provided in the rectangular pattern, and a reflection multilayer film removal mark is provided between the two patterns, and the corners are formed at the corners inside the light shielding frame. A mark equivalent to the vicinity of the portion is formed. In any case, the reflective multilayer film removal mark has an equivalent part with the corner of the part of the light shielding frame formed by deleting the absorption film and the multilayer reflective film where the vertical pattern and the horizontal pattern intersect. Therefore, it includes a shape equivalent to the inner side of the light shielding portion corner formed by the deleted absorption film and multilayer reflective film.

  Although only one position measurement evaluation mark as shown in FIG. 2 is drawn in FIG. 1, a plurality of position measurement evaluation marks may be arranged on a portion of the mask blank outer peripheral portion that is not assigned to other uses.

  FIG. 3 is a cross-sectional view showing a reflective photomask 600 manufactured with a pattern that has been optimally corrected based on the compressive stress data of the reflective multilayer film.

  As the substrate 10, for example, an ultra-low expansion material (hereinafter referred to as “LTEM”) made of silicon oxide containing titanium oxide is used. As the reflective multilayer film that reflects the EUV light, when the wavelength of the exposure light is 13.5 nm, a film in which 40 to 50 pairs of molybdenum and silicon are alternately stacked at approximately 4 nm and 3 nm is used.

  Although not shown in the drawing, a film for protecting the surface of the reflective multilayer film is often formed on the surface of the reflective multilayer film 20 and is referred to as a capping layer or the like. The absorption film 30 is a substance having a property of absorbing EUV light. For example, a film containing tantalum as a main component is used and may have a multilayer structure for the purpose of increasing the sensitivity of pattern defect inspection.

In EUV lithography, the exposure light is not perpendicular to the reflective photomask but is slightly inclined, for example, from the direction in which the principal ray is inclined by about 6 °. For this reason, the amount of shadows varies depending on the angle formed by the contour of the pattern and the incident surface. Since such an effect affects the shape and dimensions of the transfer pattern, it must be corrected on the reflective photomask pattern. If the thickness of the absorption film is large, this correction amount becomes large. From this viewpoint, it is preferable that the absorption film 30 is as thin as possible.

  When the absorbing film 30 is thinned, the contrast of the transferred image is lowered, but the phase of the light reflected on the surface of the absorbing film 30 and the light reflected on the surface of the reflective multilayer film 20 is 180 ° as in the halftone mask in the conventional photomask. If they are shifted, good contrast can be obtained on the wafer surface. However, when the absorption film 30 is thinned in this way, the light incident on the outside of the pattern region on the reflective photomask reaches the adjacent chip region on the wafer. The outside of the pattern area is masked by a member called a reticle mask blade mounted on the exposure apparatus, but complete masking is difficult.

  Therefore, an EUV mask has been proposed in which the reflectance around the pattern region on the reflective photomask is lowered. If the reflective multilayer film is removed from the entire surface other than the pattern region, it becomes difficult to form alignment marks and the like arranged around the pattern. For this reason, there are many examples in which a frame-like low reflection region is provided so as to surround the pattern region, which is called a light shielding frame or a light shielding band.

  Typical examples of the shape of the light shielding frame include those in which the reflective multilayer film 20 is removed to reduce the reflectivity of EUV light, and those in which a light shielding material is further laminated on the light shielding frame portion. The former is more advantageous from the viewpoint of preventing the occurrence.

  When the reflective multilayer film is etched away in a frame shape, the compressive stress is released at the end face where the multilayer film is interrupted as described above. Comparing the elastic modulus of the glass used as the LTEM and the reflective multilayer film 20, the reflective multilayer film 20 is several times larger. For this reason, the reflective multilayer film 20 is deformed in a direction in which the reflective multilayer film 20 extends from the center of the substrate to the outside inside the substrate than the light shielding frame 21, and toward the inside where the center of the substrate is located outside the light shielding frame 21; The glass substrate and other films will stop against the deformation that accompanies this, and will stop at the point where the repulsive forces balance.

  If the elastic modulus of the substrate is high, the amount of deformation can be reduced, but it is extremely difficult to greatly change the elastic modulus while keeping the thermal expansion coefficient regarded as a physical property low. In addition, providing a layer of a material having a high elastic coefficient between the glass substrate surface and the reflective multilayer film has the effect of reducing the amount of deformation, but it becomes extremely difficult to polish the substrate surface flatly. .

  Such deformation can be calculated by structural analysis simulation. As the physical property values of the LTEM and the reflective multilayer film 20, for example, those disclosed in Non-Patent Document 1 can be used. For example, it can also measure using techniques, such as nanoindentation.

  The stress of the reflective multilayer film 20 can be measured from the amount of deflection caused by the stress by measuring the flatness of the substrate surface before and after the reflective multilayer film 20 is formed. For example, an equation called a Stoney equation representing the relationship between the radius of curvature and stress may be applied, or more precisely, it may be obtained by fitting with a calculation result by a structural analysis program such as a finite element method.

  Thus, in the orthogonal coordinate system as shown in FIG. 4 with the center of the 6-inch square substrate surface as the origin, under the boundary condition that the position of the substrate center does not change, each point on the X axis is in the X direction. FIG. 5 shows the result of calculating the displacement amount. Here, the light shielding frame has a width of 2 mm from 52 mm to 54 mm in the X direction from the center of the substrate.

  The reason why the amount of displacement increases linearly from the center of the substrate toward the end is that the entire substrate is bent in a convex shape due to the compressive stress of the reflective multilayer film 20. FIG. 6 is a result obtained by subtracting the result of calculating the amount of displacement in the X direction in the same manner without the light shielding frame 21 from the result of FIG. 5, and represents the difference in the amount of displacement in the X axis depending on the presence or absence of the light shielding frame 21. Will be.

  On the inner side of the light shielding frame, the amount of deviation to the outer side increases rapidly as it approaches the end of the light shielding frame. Further, the deviation amount changes inward by substantially the same amount outside the light shielding frame. The amount of shift is generally negative outside the light shielding frame, which can be understood as the fact that the formation of the light shielding frame alleviates the force that stretches the entire substrate surface outward.

  If the material is the same for the negative offset amount, there is a correlation between the stress of the film and the width of the light shielding frame. The greater the stress and the larger the width of the light shielding frame, the larger the offset amount.

  FIG. 7 shows the result of calculation for FIG. 6 limited to the vicinity of the inner edge of the light shielding frame. The reason why the maximum displacement amount is smaller than that in FIG. 6 is that the calculation conditions are slightly different. In FIG. 7, the displacement amount in the X direction has a peak at a distance of about 0.1 μm from the end of the light shielding frame. It can be understood that this is because the absorption film formed on the reflective multilayer film has a small internal stress, and therefore a force that pulls the upper end inside the light shielding frame inward acts.

  The calculation result shown in FIG. 7 closely reproduces the result of actually measuring the position of the pattern arranged in the vicinity of the light shielding frame, and sufficient reliability can be obtained by appropriately adjusting the physical property value of the absorption film.

  In order to carry out such calculation using a structural analysis program based on the finite element method, for example, it is necessary to input a film stress as an initial value. The stress of the film can be calculated from the amount of deflection by measuring the surface shape before and after forming the reflective multilayer film, for example. Further, since the thermal expansion coefficient of the substrate is extremely small, the stress distribution in the film thickness direction of the multilayer film may be added to the input conditions in consideration of the stress accompanying the temperature change.

  More precisely, the film stress can be set and calculated in various ways, and the shift amount at each position of the light shielding frame end can be accumulated as a database. Stress can be acquired more accurately by collating with such a database.

 Therefore, a position measurement pattern 34 is formed on the absorption film outside the light shielding frame that is not used for pattern formation, and after the reflective multilayer film in the region 35 in the vicinity thereof is removed by etching, the position variation amount is measured. For example, the stress information of the film can be extracted, and by using the information, information on the positional deviation inside the light shielding frame can be obtained by simulation calculation. Further, a database may be constructed so that the position displacement information on the inside can be output at the time of collation with the database.

  Further, even if the position is not the actual position of the light shielding frame 21, the positional deviation caused by the release of the stress by etching the light shielding frame is sufficiently good in the in-plane uniformity of the internal stress of the reflective multilayer film, or If the in-plane distribution is grasped with sufficient accuracy, fitting can be performed by the simulation as described above, and further, the deviation from the design value at the position where the light shielding frame is formed can be calculated.

  In the present invention, the reference of the position measurement pattern is described as a fiducial mark, but the same evaluation can be performed by forming the reference pattern on the absorption film simultaneously with the formation of the position measurement pattern.

The calculation of the amount of displacement in the X direction shown in FIGS. 5 and 6 can be obtained with high accuracy by two-dimensional calculation using the cross-sectional structure as a model, and the consistency with the actual measurement value is also good. However, in the vicinity of the four corners of the light shielding frame, sufficient accuracy may not be obtained if it is approximated to two dimensions.

  Therefore, in the present invention, the reflective film removal mark includes a convex shape of 90 ° on the inner side, which is considered to be equivalent to the vicinity of the corner portion inside the light shielding frame, and a position measurement mark is arranged in the vicinity thereof, By optimizing the consistency with the simulation calculation and constructing the database, the position accuracy of the entire pattern area can be improved.

  The pattern position is affected by the holding state of the mask. In the pattern position measuring apparatus, it is typically supported at three points near the edge of the back surface of the mask substrate. Changes in the pattern position caused by the deflection of the mask substrate due to gravity are affected by these three support points, but this can also be corrected, and a commercially available position measuring apparatus has a correction function.

  However, a procedure for correcting that the amount of deflection due to gravity changes due to the formation of the light shielding frame has not been disclosed so far. According to the present invention, since the position displacement due to the holding state of the mask substrate is included, correction with higher accuracy is possible.

  Further, in the state of being attracted to the electrostatic chuck in the exposure apparatus, it is not influenced by gravity, but is affected by the flatness of the electrostatic chuck and the friction at the time of suction. The local position change in the vicinity of the edge of the light shielding frame due to the release of the stress of the reflective multilayer film is almost absorbed by the deformation of the substrate because the elastic coefficient of the substrate is relatively small and the thickness is as large as 6.35 mm. Therefore, there is no significant change before and after adsorption to the electrostatic chuck.

  However, a negative offset occurs outside the light shielding frame as shown in FIG. 6 when the bottom surface of the substrate can be freely deformed, and this amount of offset decreases when attracted to the electrostatic chuck. This amount of change can also be predicted with sufficient accuracy by the same simulation as described above.

  An example of the calculation result is shown in FIG. FIG. 11a) is a calculation result of virtually floating in the air without receiving an external force, and FIG. 11b) applies a force simulating electrostatic force so that the back surface of the substrate is in close contact with the electrostatic chuck. The state is calculated.

  In this way, exposure with high pattern position accuracy can be realized in the exposure process by performing correction including consideration of pattern position displacement due to differences in the holding state of the mask substrate.

  In the first embodiment of the present invention, a reflective photomask blank 501 having a positional deviation measuring pattern outside the light shielding frame and having relative position information with respect to the fiducial mark 42, and the reflective photomask blank 501 are provided. It is a manufacturing method.

  In view of the purpose, the fiducial mark 42 is naturally formed in the defect inspection of the reflective multilayer film 20. Hereinafter, an example of the reflective photomask manufacturing process of the present invention will be described with reference to FIG. A known cleaning process or heat treatment process may be appropriately incorporated between each process, and the order of possible parts may be changed.

  First, a low expansion glass substrate 10 having a sufficiently flat surface is prepared (see FIG. 8A). The reflective multilayer film 20 is formed on one of the main planes, and the conductive film 50 is formed on the back surface thereof (see FIG. 8B). Although not shown in the figure, a thin film may be formed for some purpose between the reflective multilayer film and the glass substrate.

  Next, a resist film 400 is applied on the reflective multilayer film 20 (see FIG. 8C), and exposed and developed by a known lithography technique to obtain a resist pattern 41 for forming a fiducial mark 42 (FIG. 8). 8 (d)).

  Next, a part or all of the depth of the reflective multilayer film 20 is removed by etching to form a fiducial mark 42, and the remaining resist film is removed (see FIG. 8E). Here, a defect inspection of the reflective multilayer film 20 is performed to obtain relative position information with respect to the fiducial mark 42 (see FIG. 8F).

  The fiducial mark is formed by removing a part of the multilayer film by lithography, but other energy beam irradiation may be used, or a film is separately deposited on the multilayer film to form a pattern. The present invention does not limit the method of forming fiducial marks.

  Next, the absorption film 30 is formed on the reflective multilayer film 20 (see FIG. 8G). Since the fiducial mark 42 is hidden when the absorbing film 30 is formed, a resist 401 is applied to remove the absorbing film 20 at the fiducial mark 42 (see FIG. 8H), and the fiducial mark 42 is formed by a lithography process. A resist pattern 43 in which the dual mark portion is exposed is obtained (see FIG. 8I).

  An embodiment of the present invention is characterized in that, in this lithography process, in addition to the fiducial mark 42, a resist pattern 44 for position measurement and a reflective multilayer film removal mark 45 are continuously exposed (see FIG. 8 (j)). As a result, the absorption film is etched to expose the fiducial mark 42, and at the same time, the position measurement mark 34 and the reflection multilayer film removal mark 35 for position shift inspection can be simultaneously formed (FIG. 8 (k)). reference). Therefore, although the patterns are separately formed in (i) and (j) of FIG. 8, it can be carried out in a single development step.

  At this point, the best direction for arranging the reflective multilayer defect so that the position of the defect of the reflective multilayer film can be adjusted by pattern position adjustment or pattern correction is unknown. Considering the provision of a frame, the position measurement mark 34 is located at a position where it does not interfere with a pattern arranged for various purposes around the reflective photomask outside the transfer region, no matter which direction the reflective photomask substrate is rotated. The reflective multilayer film removal mark 35 for position shift inspection needs to be arranged.

  Since the required accuracy differs between the pattern 43 for exposing the fiducial mark 42 and the position measurement mark 34, unlike the above, the pattern 43 for exposing the fiducial mark 42 and the position measurement mark 34 are different exposure apparatuses. It is good also as a process using.

  As one embodiment of the present invention, the step of etching and removing the reflective multilayer film 20 in the region of the reflective multilayer film removal pattern 45 arranged in the vicinity of the position measurement pattern, ie, from (l) of FIG. o) including a process.

  Reference numeral 402 in FIG. 8L denotes a resist film, which exposes and develops the reflective multilayer film removal pattern 45, which is a resist pattern for etching the reflective multilayer film (see FIG. 8M). Next, etching is performed under the same conditions as those for removing the reflective multilayer film and forming the light shielding frame (see FIG. 8 (n)). Further, when a capping layer is provided on the surface of the reflective multilayer film 20, a step of etching the capping layer may be added as necessary.

  As shown in FIG. 2a), the reflective multilayer film removal mark 35 for misregistration inspection, which is a region for etching the reflective multilayer film 20, is shown in a shape obtained by cutting a square or a part of a rectangle into a rectangle, or in FIG. 2b). In this way, a square or rectangular frame shape is used. The length of one side is preferably 1 mm to 4 mm. If the size is too small, the area that can be regarded as almost the same as the straight part of the light shielding frame cannot be taken sufficiently, and it cannot be regarded as equivalent to the corner part of the light shielding frame. There is a risk that it will not be obtained. On the other hand, if it is too large, the opening may affect the position accuracy of other patterns.

  The position measurement mark 34 is preferably formed over a range of 0.1 μm to 1 mm from the end of the region of the reflective multilayer film 20 to be removed.

  This is because, as shown in FIG. 7, there is a point where the absolute value of the positional deviation amount becomes maximum in the very vicinity of the end portion of the reflection multilayer film 20 removal region, and this range is accurately grasped. This maximum point is at a position of about 20 μm of the reflective multilayer film, and the amount of positional deviation gradually decreases as the distance from the maximum point increases. In consideration of the measurement error of the position measuring device, if the measurement is performed up to a portion about 1 mm away from the end portion, it is possible to obtain sufficient information on the displacement due to stress release.

  Therefore, by measuring and comparing the position of the position measurement mark in the state 500 in FIG. 8K and the state 501 in FIG. 8O with the resist removed, the stress of the reflective multilayer film formed on the substrate is measured. It is possible to grasp the amount of misalignment based on the influence of. In this case, an approximate function may be obtained according to the distance between the reflective multilayer film removal mark 35 and the position measurement mark 34, or by fitting with a model using the structural analysis program, the reflection multilayer film etching part may be removed from the end of the reflective multilayer film etching part. Data on the amount of displacement according to the position may be obtained.

  The reflection type photomask pattern data can be corrected using a known technique so as to cancel out the pattern shift amount obtained in this way.

  A reflective photomask blank having a fiducial mark and position correction information according to the present invention can be obtained in the state 501 shown in FIG. Further, the reflective photomask blank of the present invention includes a state 502 in which a resist used for drawing a mask pattern is applied thereon (see FIG. 8 (p)).

  The corrected pattern can be drawn on the resist formed on the absorption film, and the absorption pattern 36 can be obtained by development, etching, and resist removal, resulting in a reflective photomask 503 that does not have a light shielding frame ( (See FIG. 8 (p), (q), (r), (s)). At this time, a pattern defect inspection is performed, and the pattern defect is corrected as necessary.

  Further, a resist film is formed thereon (see FIG. 8 (u)), pattern formation is performed so that the light shielding frame is exposed (see FIG. 8 (v)), and the reflective multilayer film is etched (see FIG. 8 (v)). (See FIGS. 8 (w) and (x)). Since it is important to select conditions that do not damage the reflective multilayer film as the etching conditions for the absorption film, etching of the absorption film and the reflective multilayer film is generally a combination of multiple conditions. If the conditions capable of etching both the absorption film and the reflective multilayer film can be selected, it is possible to continuously etch the absorption film and the reflective multilayer film.

  After the above steps, the remaining resist is removed and washed to obtain the reflective photomask 600 having the light shielding frame. Even if the light shielding frame is formed by removing the reflective multilayer film, the vicinity of the light shielding frame is obtained. A highly accurate reflective photomask that suppresses a decrease in position accuracy can be obtained (see FIG. 8Y).

  In the present invention, the positional deviation amount outside the light shielding frame formed by removing the multilayer film as shown in FIG. 6 can be extracted together with the positional deviation amount data.

  Such positional variation is affected by the holding state of the substrate. For example, when holding three points near the edge of the substrate as supporting points, the amount of deflection due to the gravity of the substrate slightly changes before and after the formation of the light shielding frame, so that it is in the vicinity of the light shielding frame formed by removing the multilayer film. In the inspection of the positional accuracy of the formed pattern, it is possible to accurately determine the quality of the product by using a value in consideration of a variation in the deflection amount due to gravity as a reference.

  Further, by incorporating a condition in which the substrate is attracted to the electrostatic chuck in addition to the calculation shown in FIG. Also, the difference between the position of the pattern with respect to the substrate center when it is installed in the exposure apparatus and the position of the pattern with respect to the substrate center when the pattern is supported at three points near the edge of the substrate by the mask pattern position inspection apparatus. Can also be calculated.

  By performing the pattern position inspection using the above information, it is possible to accurately determine the quality of the pattern position accuracy of the reflective photomask product.

  ULE (registered trademark, manufactured by Corning) is used as an ultra-low thermal expansion glass substrate, and after polishing the surface flatly, a reflective multilayer film in which molybdenum and silicon are alternately laminated on one side of the main plane, and chromium on the back side. A substrate on which a component film was formed was prepared.

  Next, a fiducial mark was formed on the reflective multilayer film using a known lithography technique, and a defect inspection of the reflective multilayer film surface was performed. The detected coordinates were recorded as a relative position to the fiducial mark.

  Next, an absorption film mainly composed of tantalum was formed on the reflective multilayer film. In order to form the fiducial mark visibility, the pattern for exposing the fiducial mark portion and the multilayer film removal mark 35 for misalignment inspection are formed in the empty area around the reflective photomask. A resist film including the reflective multilayer film removal pattern 45 and the pattern 44 for forming the position measurement mark was formed.

  Using the resist pattern as a reflective photomask, the fiducial marks were exposed and easily visible, and the misalignment measurement pattern and the reflective multilayer film removal pattern 45 area were also exposed.

  In this state, the position of the misalignment measurement pattern was measured with a pattern position measurement device LMS IPRO (manufactured by VISTEC).

  Next, a resist pattern was formed so that only the reflective multilayer film removal pattern 45 was exposed, and the reflective multilayer film was removed by etching.

  In this state, the position of the misalignment measurement pattern was measured in the same manner as described above, and the amount of change in position before and after removing the reflective multilayer film was obtained. The positional deviation measurement pattern has a distance from the reflective multilayer film removal region between 1 μm and 1 mm, and the same results as in FIGS. 6 and 7 were obtained from the respective measurement results.

  Further, the X and Y direction distances and deviation amounts from the corners of the light shielding frame are determined based on the X and Y direction pattern deviation amounts of the positional deviation measurement pattern in the vicinity of the corners provided in a convex shape inside the reflective multilayer film removal mark. The components in the X and Y directions were extracted.

  The relationship between the distance from the edge of the reflective multilayer film etching region and the amount of positional deviation was approximated by a polynomial, and the drawing position of the reflective photomask pattern data was corrected based on this.

  Next, a resist was coated, a pattern subjected to the above correction was formed by electron beam drawing, and a reflective photomask was produced through the steps of etching the absorption pattern and removing the resist.

  Subsequently, a resist was applied to form a light shielding frame pattern 46, the light shielding frame pattern 46 was exposed by a laser drawing apparatus, and a reflective photomask having a light shielding frame was obtained through development, etching, and resist removal processes. When the positional accuracy of the reflection type photomask obtained in this way was measured, the difference from the design value was within an allowable range even in the vicinity of the light shielding frame 21, and the structure analysis program for the state of being attracted to the electrostatic chuck It was confirmed that it was well within the allowable range even when predicted by calculation using.

  According to the present invention, in manufacturing a semiconductor device or the like using a lithography technique using EUV light, there is little misalignment even in the peripheral region of the circuit pattern, and generation of defective products due to poor alignment can be suppressed.

DESCRIPTION OF SYMBOLS 10 ... LTEM board | substrate 20 ... reflective multilayer film 21 ... light shielding frame 22 ... light shielding frame 30 deform | transformed by stress ... absorption film 34 ... position measurement mark 35 ... reflection multilayer film removal mark 36 for position shift inspection ... mask pattern 40 ... resist film 41 A resist pattern 42 for forming a fiducial mark ... A fiducial mark 43 ... A pattern 44 for removing an absorption film at a fiducial mark position ... A resist pattern 45 for forming a position measurement mark ... A reflective multilayer Resist pattern 46 for forming a film removal mark ... resist pattern 50 for forming a light shielding frame ... backside conductive film 100 ... reflective photomask blanks 401, 402, 403, 404 ... resist film 501 ... positional deviation information due to reflective multilayer film stress Reflective photomask blank 502 with reflective multilayer film stress An example of a reflective photomask example 601 ... the invention of the reflective photomask reflective photomask 600 ... present invention having no resist film with a photomask blank 503 ... light shielding frame provided with the positional displacement information that

Claims (5)

A reflective photomask blank having a reflective multilayer film on one surface of the substrate, an absorption film on the reflective film, and a back surface conductive layer on the other surface,
A mark for measuring the positional relationship between the fiducial mark and the fiducial mark is provided on the outer periphery of the reflective photomask blank and the positional relationship with the fiducial mark is measured. A region where the absorption film and the reflective multilayer film are partially removed is provided in the vicinity, and the shape obtained by partially removing the absorption film and the reflective multilayer film has a convex shape of 90 degrees inside. Reflective photomask blank.   A reflective photomask blank, wherein a resist is coated on the absorption film of the reflective photomask blank according to claim 1.   The mark difference information for measuring the positional relationship with the fiducial mark before and after providing the region where the absorption film and the reflective multilayer film are partially removed is added. A reflective photomask blank according to 1.   A method of manufacturing a reflective photomask using the photomask blank according to claim 3, wherein when the influence generated when a light shielding frame is formed is corrected based on the difference information, it is attracted to an electrostatic chuck. Manufacturing a reflective photomask characterized in that it includes a procedure that takes into account the difference in substrate state between when the position accuracy of a photomask pattern is measured in an unapplied state and when it is attracted to an electrostatic chuck in an exposure apparatus Method.   A reflective photomask manufactured according to the method for manufacturing a reflective photomask according to claim 4.