JP2018072665A - Manufacturing method of reflection type mask blank and reflection type mask blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a high quality reflection type mask blank without generating phase defect.SOLUTION: There is provided a manufacturing method of a reflection type mask blank including following 1) to 6) processes in the order. 1) a process for making a multilayer reflection layer having less layer than final layer number. 2) a process for defect inspecting a surface shape of the multilayer reflection layer having less layer than the final layer number. 3) a process for removing area including defects detected by the defect inspection in the multilayer reflection layer made in the 1) process. 4) a process for correcting projection shaped or recess shaped defects exposed in the 3) process, which cause defects detected in the 2) process. 5) a process for additionally making the multilayer reflection layer. 6) a process for polishing removing an area of the multilayer reflection layer having more layers than the final layer number.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a reflective mask blank manufacturing method and a reflective mask blank for producing a reflective mask used in lithography using extreme ultraviolet (EUV) as a light source.

(Description of EUV lithography)
In recent years, with the miniaturization of semiconductor devices, EUV lithography using an EUV light source having a wavelength of around 13.5 nm has been proposed. Since EUV lithography has a short light source wavelength and very high light absorption, it is necessary to perform transfer in a vacuum chamber of an exposure apparatus. In the EUV wavelength region, the refractive index of most substances is slightly smaller than 1. For this reason, the EUV lithography cannot use a transmission type refractive optical system which has been used conventionally, and becomes a reflection optical system. Accordingly, a conventional photomask (hereinafter referred to as a mask) cannot be used as a photomask (hereinafter referred to as a mask) and must be a reflective mask.

(Description of reflective mask blank and mask structure)
A reflective mask blank 500 as a base of the reflective mask as described above is as shown in FIG. 8, and has a high reflectance with respect to the light source wavelength on a low thermal expansion substrate (hereinafter referred to as a substrate as appropriate) 50. A multilayer reflective layer 51 (M) and an absorption film 55 having a light source wavelength are sequentially formed by a normal sputtering method. When processing from the reflective mask blank 500 to the reflective mask 560, the absorption film 55 is partially removed by EB (electron beam), laser lithography and etching techniques, and the absorption film pattern 55a and the high reflection portion 57 are formed. A circuit pattern 56 is formed. The optical image reflected by the reflective mask 560 thus manufactured is transferred onto a semiconductor substrate (hereinafter referred to as a wafer) through a reflective optical system.

  A capping film (protective film) on the multilayer reflective layer, an absorption film on the capping film, and a buffer film (buffer film) formed between the capping film and the absorption film, and a lithography resist on the absorption film Although the formed form may be called a blank, in the present invention, a form in which up to a multilayer reflective layer is formed on a low thermal expansion substrate is particularly called a reflective mask blank.

(Defects that occur in reflective mask blanks)
The circuit pattern line width of a reflective mask for EUV lithography is very small, about several tens of nm, and is easily affected by defects generated in the reflective mask. The defect of the reflective mask is a pattern defect generated in the circuit pattern when processing from the reflective mask blank to the reflective mask, and is generated on the substrate surface by polishing of the low thermal expansion substrate when manufacturing the reflective mask blank. There are two types of phase defects due to irregularities or particles or foreign matter generated on the substrate or during the formation of the multilayer reflective layer.

  For pattern defects, after forming a circuit pattern, a photomask correction machine is used to irradiate FIB (Focused Ion Beam = focused ion beam) or EB in a specific gas atmosphere to perform etching or deposition (partial formation). The film can be repaired. On the other hand, the phase defect is a phenomenon in which the phase shift of the wave fronts of the normal part and the defective part of the reflected light generated by the interference of the interface reflection of the multilayer film is superimposed, so that the repair is very difficult.

FIG. 1 shows a case where a convex defect (represented by a rectangular cross-section in this case) that is a phase defect of a reflective photomask blank is present on the substrate (13a), FIG. ) is a schematic sectional view of (13b) in the multilayer reflective layer, FIG. 1 (c), the height of those defects as horizontal axis, normal portion reflected light R ₀ and defect reflected light R _d It is a characteristic view which shows the result of having calculated the phase difference of. Here, the multilayer reflective layer is an EUV mask blank obtained by alternately stacking 40 pairs (80 layers) of Si (silicon: 4.2 nm thickness) and Mo (molybdenum: 2.8 nm thickness) alternately. The substrate convex defect 12a and the convex defect 12b in the multilayer film that cause the defect are both calculated as Si particles, the substrate material is quartz close to a low thermal expansion substrate, and the wavelength is 13.5 nm. Moreover, the value of Table 1 is used for the optical constant of the material used by calculation including the calculation mentioned later.

  In FIG. 1 (c), the solid line A has Si particles on the substrate, and when 40 pairs of multilayer reflective layers are laminated thereon, the alternate long and short dash line B has Si particles on which 20 pairs of multilayer reflective layers are laminated. When 20 pairs of multilayer reflective layers are stacked, dotted line C indicates a case where 30 pairs of multilayer reflective layers are stacked, Si particles are present, and 10 pairs of multilayer reflective layers are stacked thereon. It can be seen that the phase difference decreases as the Si particles move away from the substrate and approaches the surface of the multilayer reflective layer, but in any case, a large phase difference is generated with the height of the Si particles.

(Invalidation of phase defect by Defect Avoidance technology)
As one of techniques for avoiding the influence of phase defects, there is a technique called Defect Avoidance that creates a circuit pattern while avoiding a phase defect portion (for example, Patent Document 1). In this method, an alignment marking is applied to the substrate, and then a multilayer reflective layer is formed. Thereafter, the relative coordinates from the alignment of the phase defect occurring in the reflective mask blank are read, and the circuit pattern data is rotated by 90 degrees, 180 degrees, 270 degrees to avoid the phase defect coordinates, or the circuit pattern data is Adjustment is made so that an important circuit pattern does not come to the phase defect portion by a method such as slightly translating or changing circuit pattern data. However, the number of phase defects that can be avoided by this method is several, and it is impossible to deal with complicated circuit patterns.

(Repair of phase defects using compensation repair technology)
As another method to avoid the influence of the phase defect, paying attention to the characteristic that the EUV light reflectance of the phase defect portion is lowered, the effect of the phase defect is optically corrected by etching correction of the absorption film pattern adjacent to the phase defect. In other words, a method called compensation repair has been proposed that cancels the process and improves the circuit pattern transferred onto the wafer (Patent Document 2).

  However, in the method of Patent Document 2, if a phase defect having a size that extends over two or more lines occurs in a circuit pattern, for example, Line & Space, it is difficult to correct in principle. Further, since the compensation repair requires a process of simulating the influence on the wafer after exposure transfer and determining the etching amount of the absorption film pattern, there is a concern that the productivity of the reflective mask is lowered. In addition, since it is necessary to develop infrastructure such as simulation software, there is a concern about an increase in cost.

JP 2013-179270 A Japanese translation of PCT publication No. 2002-532738

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to provide an uneven surface of a substrate caused by polishing during the production of a reflective mask blank, or on a low thermal expansion substrate. In addition, the cause of phase defects such as particles and foreign matters generated during the formation of a multilayer reflective layer is removed, and a high-quality reflective mask blank is manufactured. When a reflective mask is manufactured, such as Defect Aviation and Compensatory Repair It is an object of the present invention to provide a reflective mask blank manufacturing method and a reflective mask blank that do not require a complicated process and enable production of a reflective mask with high productivity.

In order to solve the above-mentioned problem, the invention described in claim 1 is a method of manufacturing a reflective mask blank having a multilayer reflective layer on a substrate, and sequentially includes the following steps 1) to 6). This is a method for manufacturing a reflective mask blank characterized by the following.
1) A step of forming a multilayer reflective layer fewer than the final number of layers.
2) A step of inspecting the surface shape of the multilayer reflective layer that is less than the final number of layers.
3) The process of removing the area | region containing the defect detected by the said defect inspection of the multilayer reflection layer formed into the film of 1).
4) A step of correcting the convex or concave defect that is the cause of the defect detected in the step 2) and is exposed in the step 3).
5) A step of additionally forming a multilayer reflective layer.
6) A step of polishing and removing a region of the multilayer reflective layer that has become larger than the final number of layers.

  The invention according to claim 2 is the method for producing a reflective mask blank according to claim 1, wherein the steps 1) to 5) are repeated.

  The invention according to claim 3 is characterized in that any one of an electron beam, a focused ion beam, a laser, and a probe is used to correct the convex or concave defect in the step 4). This is a manufacturing method of the reflective mask blank described in 2).

  The invention according to claim 4 is a reflective mask blank having a multilayer reflective layer on a substrate, wherein the reflective mask blank has a rotational polishing mark on the surface of the multilayer reflective layer. It is.

  According to the present invention, since the reflective mask blank manufacturing method includes the process as defined in claim 1, unevenness of the substrate generated by polishing during the production of the low thermal expansion substrate, or formation of the multilayer reflective layer on the low thermal expansion substrate The cause of phase defects such as particles and foreign matters generated inside is removed, and a high-quality reflective mask blank that does not generate phase defects can be manufactured, and complex defects such as Defect Aviation and Compensatory Repair can be used when manufacturing reflective masks. Therefore, it is possible to reduce the cost of manufacturing the reflective mask and improve the productivity.

When the convex defect of the reflective photomask blank is (a) on the substrate, (b) a schematic cross-sectional view when in the multilayer reflective layer, and (c) normal part reflected light and defect with respect to the height of the defect It is the characteristic view which computed the phase difference of the partial reflected light. It is a manufacturing process flowchart of the reflective mask blank of this invention. It is a schematic cross section which shows the manufacturing process (when there exists a board | substrate convex defect) of the reflective mask blank of this invention. It is a schematic cross section which shows the manufacturing process (when there exists a board | substrate concave defect) of the reflective mask blank of this invention. It is a schematic cross section which shows the manufacturing process (when there exists a convex defect in a multilayer film) of the reflective mask blank of this invention. It is the characteristic view which computed the ultraviolet-ray (DUV light, EUV light) reflectance with respect to the number of pairs of a multilayer reflective layer. (A) Phase difference between normal part reflected light and defect part reflected light with respect to the convex part height on the outermost surface of the multilayer reflective layer, (b) EUV light reflectance with respect to the same surface roughness, (c) Substrate surface roughness (= multilayer) It is the characteristic view which calculated the EUV light reflectance with respect to (reflection layer interlayer roughness). It is a schematic cross section showing the structure of the reflective mask blank and the reflective mask and part of the manufacturing process.

  Hereinafter, a reflective mask blank manufacturing method and a reflective mask blank according to an embodiment of the present invention will be described in detail. In addition, the same code | symbol is attached | subjected about the same component unless there is a reason for convenience, and the overlapping description is abbreviate | omitted. Also, in the drawings used in the following description, in order to make the features easy to understand, the portions that become the features may be shown in an enlarged manner, and the dimensional ratios of the respective constituent elements are not the same as the actual ones.

(Production process flow of the reflective mask blank of the present invention)
FIG. 2 shows a flow chart of the manufacturing process of the reflective mask blank of the present invention. First, a multilayer reflective layer is formed on a low thermal expansion substrate by sputtering (referred to as N layer) sputtering (STEP 1), and surface shape defect inspection is performed on the entire surface (STEP 2). Therefore, SEM (scanning electron microscope) measurement is performed on the detected defect, and the shape and size of the unevenness are confirmed (STEP 3). Thereafter, the region of the multilayer reflective layer including the defective portion is removed using a correction machine or the like to expose the defect (STEP 4). Thereafter, if the defect has a concave shape, the deposition correction is performed by a photomask correcting machine (STEP 5). If the defect has a convex shape, an etching correction is performed (STEP 5 '), and the defect is removed.

  Next, in order to confirm the corrected shape, surface roughness is measured with an AFM (atomic force microscope), and RMS (Root Mean Square) is less than or equal to a set allowable value. It is determined whether the value is out of range (STEP 6). If it is less than the allowable value, the correction is successful (YES), and if it is out of the allowable value (NO), the correction, AFM measurement, and determination are repeated until YES. Here, the allowable value may be set as appropriate according to the type of circuit pattern to be transferred and formed by EUV exposure, the line width, and transfer conditions. Thereafter, the N-layer sputtering in STEP 1 to the RMS judgment in STEP 6 are repeated k times, and then the (k + 1) th film formation is performed, and the portion that has not been corrected once is more than the target M (= N × k) layer. Sputter deposition of the multilayer reflective layer with many layers is completed (STEP 7).

  In the above, k = 1 is the inspection and correction for the concave / convex defect of the substrate generated by polishing at the time of manufacturing the substrate, and k = second and subsequent inspection and correction for defects such as particles and foreign matters generated during the formation of the multilayer reflective layer. It is. Assuming that corrections are made one by one up to k times, the number of correction points will eventually be k, but since the normal correction points are small, the k correction points are at different positions, and k times. In the film formation up to this point, the number of layers at these correction points is N × (k−1).

  Therefore, after STEP7, the particles generated in the (k + 1) th film formation and the portion where the film was thickened (excessively) by the N layer rather than the M (= N × k) layer without any correction are subjected to CMP polishing. It may be removed by (Chemical Mechanical Polishing) (STEP 8). By the above, the reflective mask blank of this invention provided with the multilayer reflective layer without the concave defect or convex defect which causes a phase defect is completed.

In the above description, an example of forming the target M multilayer reflective layer has been described in which each N layer is repeated k times to form the M layer. However, it is not always necessary that each N layer is formed. If the generation of particles and foreign matter is small (if it is large), the number of layers may be increased by a smaller number than the N layer after the second time, and finally M layers may be formed. In this case, the largest number of the multilayer reflective layers formed excessively is equal to the number of layers formed when the largest number is formed.

(Manufacturing process of the reflective mask blank of the present invention when there is a substrate convex defect)
FIG. 3 is a flow chart of the manufacturing process described with reference to FIG. 2. There is a convex defect 22 generated by polishing during the production of the substrate 20, and for the sake of simplicity, only k = 1 is assumed. 4 is a schematic cross-sectional view showing a process of manufacturing 240. FIG.

  First, when an N-layer multilayer reflective layer 21 (N) is formed on the substrate 20 by sputtering, a reflective mask blank 200 (with a convex phase defect 23) shown in FIG. Thereafter, defect inspection is performed to detect a shape defect that becomes the phase defect 23, and then SEM measurement is performed based on the inspection result to confirm the shape and size of the defect. Thereafter, the region of the multilayer reflective layer including the defective portion is removed using a correction machine or the like, the defect 22 is exposed as 21 (N) a, and the multilayer reflective layer in the defective region shown in FIG. A reflective mask blank 210 is obtained.

  Next, the convex defects 22 on the substrate are removed by etching using a photomask correcting machine, and a convex mask 220 having a corrected convex defect shown in FIG. 3C is obtained. Thereafter, the surface roughness after the defect correction is measured with an AFM, and after confirming that the RMS is within an allowable value, the target M layer is formed as a multilayer reflective layer, and the excess shown in FIG. A reflective mask blank 230 having the multilayer reflective layer 21 (+ N) a is obtained. Finally, the excess multilayer reflective layer 21 (+ N) a is polished by CMP to obtain the reflective mask blank 240 of the present invention after CMP polishing shown in FIG. 3 (e).

(Manufacturing process of the reflective mask blank of the present invention when the substrate has a concave defect)
FIG. 4 is a flow chart of the manufacturing process described with reference to FIG. 2, and there is a concave defect 32 such as a pit generated by polishing during the production of the substrate 30. For the sake of simplification, only k = 1 is assumed. It is a schematic cross section which shows the process of manufacturing the mask blank 340.

  First, when an N-layer multilayer reflective layer 31 (N) is formed on the substrate 30 by sputtering, a reflective mask blank 300 (with a concave phase defect 33) shown in FIG. 4A is obtained. Thereafter, defect inspection is performed to detect a shape defect that becomes the phase defect 33, and then SEM measurement is performed based on the inspection result to confirm the shape and size of the defect. Thereafter, the region of the multilayer reflective layer including the defective portion is removed using a correction machine or the like to expose the defect 32 as 31 (N) a, and the multilayer reflective layer in the defective region shown in FIG. 4B has been removed. A reflective mask blank 310 is obtained.

  Next, the concave defect 32 on the substrate is filled with a photomask correction machine to form a deposition unit 34, and a concave defect corrected reflective mask blank 320 shown in FIG. 4C is obtained. Thereafter, the surface roughness after the defect correction is measured with an AFM, and after confirming that the RMS is within an allowable value, the target M layer is formed as a multilayer reflective layer, and the excess shown in FIG. A reflective mask blank 330 having the multilayer reflective layer 31 (+ N) a is obtained. Finally, the excess multilayer reflective layer 31 (+ N) a is polished by CMP to obtain the reflective mask blank 340 of the present invention after CMP polishing shown in FIG. 4 (e).

(Manufacturing process of the reflective mask blank of the present invention when there are convex defects in the multilayer film)
FIG. 5 is a flow chart of the manufacturing process described with reference to FIG. 2, and there is a convex defect 42 due to particles generated after forming the N × p multilayer reflective layer. For simplicity of explanation, the remaining N layers are formed. FIG. 5 is a schematic cross-sectional view showing a process of manufacturing a reflective mask blank 440 of the present invention, which is a target M layer with a film.

  Until the multilayer reflective layer 41 (Np) of N × p layer is formed on the substrate 40 by sputtering, the shape defect that becomes the phase defect is not detected by the defect inspection, and further, the N layer is formed and the defect is detected. As a result of inspection, it is assumed that a reflective mask blank 400 with a convex phase defect 43 shown in FIG. 5A is obtained. Therefore, SEM measurement is performed based on the inspection result to confirm the shape and size of the defect. After that, the region of the N multilayer reflective layer including the defect is removed using a correction machine or the like to expose the defect 42 as 41 (N) a, and the N layer of the defect region shown in FIG. The reflective mask blank 410 from which the multilayer reflective layer has been removed is obtained.

  Next, the convex defect 42 on the multilayer reflective layer is removed by etching with a photomask correcting machine, to obtain a reflective mask blank 420 with a corrected convex defect shown in FIG. Thereafter, the surface roughness after the defect correction is measured by AFM, and after confirming that the RMS is within an allowable value, the remaining N layers are formed as a multilayer reflective layer, and the excess shown in FIG. A reflective mask blank 430 having the multilayer reflective layer 41 (+ N) a is obtained. Finally, the excess multilayer reflective layer 41 (+ N) a is polished by CMP to obtain the reflective mask blank 440 of the present invention after CMP polishing shown in FIG. 5 (e).

  The defect inspection performed in STEP 2 of FIG. 2 is preferably an optical method with a high inspection speed, and the wavelength is preferably in the ultraviolet (DUV (deep ultraviolet) light or EUV light) region. FIG. 6 is a characteristic diagram in which the reflectance of ultraviolet rays (DUV light, EUV light) is calculated with respect to the number of pairs (= number of layers / 2) of the multilayer reflective layer. Here, the materials of the multilayer reflective layer are Si and Mo as described above, the substrate material is quartz, and the values of Table 1 are used as the optical constants of the materials used in the calculation.

  As can be seen from FIG. 6, in the case of DUV light having a wavelength of 257 nm or 199 nm used in normal optical defect inspection, a high reflectance of about 30% in one pair of film formation and about 50% in two pairs of film formation. (This is due to metallic reflection of Si or Mo), and the uneven shape of the surface can be detected by dark-field optical inspection. On the other hand, in order to obtain a reflectance of 30% with EUV light, it is necessary to form about 10 pairs of films. Therefore, it is desirable to use DUV light at a stage where the number of deposited layers is small. If the reflectivity is the same, EUV light with a short wavelength is higher in resolution, so it is preferable to use a DUV light or EUV light inspection apparatus properly depending on the defect size to be detected and the particle generation status of the sputtering apparatus. .

  In the reflective mask blank manufacturing method of the present invention, CMP polishing of the multilayer reflective layer formed excessively is performed in the final STEP 8 of FIG. CMP has become an indispensable technique for planarization for high integration and high performance of semiconductors in recent years and for planarization of precision parts such as optical parts. In CMP, with both the abrasive-encapsulated polishing pad and the object to be polished rotated, a polishing liquid (slurry) is supplied to the surface of the polishing pad to perform chemical polishing with a liquid component and mechanical polishing with abrasive particles. Polishing is performed by the synergistic effect. In CMP of a metal film, a polishing liquid made of a mixture of inorganic compound particles such as alumina and silica and an oxidizing agent such as ferric nitrate and aqueous hydrogen peroxide is used.

  However, since CMP performs mechanical polishing with abrasive particles as described above, it is difficult to completely remove a polishing modified layer (damage layer) such as a polishing mark on the surface of an object to be polished. Therefore, also in the manufacturing method of the reflective mask blank of the present invention, it is expected that a rotational polishing mark will remain on the surface of the multilayer reflective layer in the final STEP 8, and there is a concern about the influence.

  7A and 7B show, in order to examine the influence of polishing marks on the surface of the multilayer reflective layer, (a) normal part reflected light and defective part reflected light of EUV light with respect to the height of the convex and concave portions on the outermost surface of the multilayer reflective layer. (B) is a characteristic diagram in which the reflectance with respect to the surface roughness is calculated. The multilayer reflective layer is made of 40 pairs of Si and Mo, and the outermost surface is made of Si, as before. From these figures, it can be seen that the effect on the phase difference and the reflectance is not a problem even if the height and surface roughness are changed on the outermost surface. For comparison, FIG. 7C shows the reflectance when the roughness of the quartz substrate surface is assumed to continue across all the layers of the multilayer reflective layer. It can be seen that the surface roughness greatly reduces the reflectivity.

  From the above, it is expected that a rotational polishing mark will remain on the surface of the multilayer reflective layer in the reflective mask produced by the method for manufacturing a reflective mask blank of the present invention. If it is, the influence on the reflectance and the phase difference is small, and any level that does not affect the line width accuracy of the absorption film pattern when masked is acceptable.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples without departing from the spirit of the present invention.

<Example 1>
Hereinafter, an embodiment of a method for manufacturing the reflective mask blank 240 of the present invention shown in FIG. 3 will be described. 40 pairs of Mo and Si (= 80 layers, total 280 nm thickness) designed to have a reflectivity of about 65% for EUV light with a wavelength of 13.5 nm on the low thermal expansion substrate 20 shown in FIG. ), The first pair (= 2 layers, total 7 nm thickness) of the multilayer reflective layer 21 (N) was formed by a sputtering apparatus. Subsequently, a defect inspection of the surface shape of the entire surface of the multilayer reflective layer 21 (N) was performed using a wavelength of 199 nm by a mask inspection apparatus, and a convex phase defect 23 having a size of about 300 nm was detected in a plan view. Next, an accurate size and shape were obtained by observation with an SEM. The pair of multilayer reflective layers 21 (N) is removed by irradiating a 1 um square region with a laser having a wavelength of 355 nm to the portion by a laser corrector, and the low thermal expansion substrate shown in FIG. Thus, a reflective mask blank 210 in which the convex defect 22 was exposed was obtained. Thereafter, etching correction of only the convex defect 22 is carried out by irradiating EB while blowing an etching gas to the 300 nm-sized convex defect 22 with a photomask EB correcting machine having a beam diameter smaller than that of the laser. The reflective defect-corrected mask blank 220 shown in 3 (c) was obtained. In order to confirm the corrected shape, the RMS roughness of a 500 nm square on the low thermal expansion substrate was measured by AFM, which was within the allowable value set to 0.45 nm. Thereafter, 40 pairs of Si and Mo (= 80 layers, total 280 nm thickness) are formed, and an excess multilayer reflective layer 21 (+ N) a (here, 1 pair = 2 layers) shown in FIG. ) To obtain a reflective mask blank 230. Next, two pairs of excess multilayer reflective layers 21 (+ N) a were polished by CMP to obtain a reflective mask blank 240 of the present invention after CMP polishing shown in FIG. 3 (e). Finally, when the surface of the multilayer reflective layer was measured with AFM, rotational polishing marks were observed, but the RMS measurement was 0.40 nm.

<Example 2>
Hereinafter, the Example of the manufacturing method of the reflective mask blank 340 of this invention of FIG. 4 is described. 40 pairs of Mo and Si (= 80 layers, total 280 nm thickness) designed to have a reflectivity of about 65% with respect to EUV light having a wavelength of 13.5 nm on the low thermal expansion substrate 30 shown in FIG. ), The first pair (= 2 layers, total 7 nm thickness) of the multilayer reflective layer 31 (N) was formed by a sputtering apparatus. Subsequently, a defect inspection of the surface shape of the entire surface of the multilayer reflective layer 31 (N) was performed using a wavelength of 199 nm by a mask inspection apparatus, and a concave phase defect 33 having a size of about 300 nm was detected in a plan view. Next, an accurate size and shape were obtained by observation with an SEM. On the low thermal expansion substrate shown in FIG. 4 (b), the pair of multilayer reflective layers 31 (N) is removed by irradiating a 1um square region with a laser having a wavelength of 355nm with a laser correction machine. Thus, a reflective mask blank 310 with the concave defect 32 exposed was obtained. Thereafter, the EB irradiation machine for the photomask having a beam diameter smaller than that of the laser is irradiated with EB while blowing the deposition gas to the 300 nm-sized concave defect 32, thereby correcting the deposition of only the concave defect 32. The concave defect-corrected reflective mask blank 320 shown in 4 (c) was obtained. In order to confirm the corrected shape, the RMS roughness of a 500 nm square on the low thermal expansion substrate was measured by AFM, and it was within the allowable value set to 0.48 nm, and therefore the determination was passed. Thereafter, 40 pairs of Si and Mo (= 80 layers, total 280 nm thickness) are formed into a multilayer reflective layer, and the excess multilayer reflective layer 31 (+ N) a (here, 1 pair = 2 layers) shown in FIG. ) To obtain a reflective mask blank 330. Next, two pairs of excess multilayer reflective layers 31 (+ N) a were polished by CMP to obtain a reflective mask blank 340 of the present invention after CMP polishing shown in FIG. 4 (e). Finally, when the surface of the multilayer reflective layer was measured by AFM, rotational polishing marks were observed, but the RMS measurement was 0.41 nm.

200, 400 ... reflective mask blanks 210, 410 with convex phase defects, reflective mask blanks 220, 420 with defect layer multilayer reflective layer removed, reflective mask blanks 230, 430 with corrected convex defects ... Reflective mask blanks 240, 440 ... Reflective mask blanks 300 after CMP polishing ... Reflective mask blanks 310 with concave phase defects ... Reflection after removal of defective multilayer reflective layers Type mask blank 320... Defect-corrected reflection type mask blank 330... Reflective mask blank 340 after multilayer reflection layer deposition reflection type mask blank 10, 20, 30, 40, 50.・ Low thermal expansion substrate
11... Multilayer reflective layer 21 (N), 31 (N), 41 (N)... Multilayer reflective layer (number of layers: N)
21 (N) a, 31 (N) a, 41 (N) a
... Multilayer reflective layers from which defects have been removed (number of layers: N)
21 (+ N) a, 31 (+ N) a, 41 (+ N) a... Excess multilayer reflective layer (number of layers: N)
41 (Np)... Multi-layer reflective layer (number of layers: N × p)
21 (M), 31 (M), 41 (M), 51 (M) ... multilayer reflective layer (number of layers: M)
12a, 22... Substrate convex defect 12b, 42... Convex defect (particles or foreign matter) in the multilayer film
13a, 13b, 23, 43... Convex phase defect 32... Substrate concave defect (pit, etc.)
33 ... recessed phase defect 34 ... deposition unit _R 0 ... normal part reflected light _R d .... defect reflected light 500 ... reflective mask blank 550 ... absorption film Reflective mask blank 560... Reflective mask 55... Absorption film
55a ... Absorbing film pattern 56 ... Circuit pattern 57 ... High reflection part

Claims (4)

A method for producing a reflective mask blank comprising a multilayer reflective layer on a substrate, comprising the following steps 1) to 6) in sequence.
1) A step of forming a multilayer reflective layer fewer than the final number of layers.
2) A step of inspecting the surface shape of the multilayer reflective layer that is less than the final number of layers.
3) The process of removing the area | region containing the defect detected by the said defect inspection of the multilayer reflection layer formed into the film of 1).
4) A step of correcting the convex or concave defect that is the cause of the defect detected in the step 2) and is exposed in the step 3).
5) A step of additionally forming a multilayer reflective layer.
6) A step of polishing and removing a region of the multilayer reflective layer that has become larger than the final number of layers.   The method of manufacturing a reflective mask blank according to claim 1, wherein the steps 1) to 5) are repeated.   3. The reflective mask blank according to claim 1, wherein the correction of the convex or concave defect in the step 4) uses any one of an electron beam, a focused ion beam, a laser, and a probe. Production method. A reflective mask blank comprising a multilayer reflective layer on a substrate, wherein the multilayer reflective layer has a rotational polishing mark on the surface thereof.