JP2013149875A - Method of manufacturing reflection type mask for euv exposure reducing influence of phase defect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a reflection type mask for EUV exposure that reduces an influence of a phase defect by precisely grasping a position of the phase defect, which grows obliquely, and arranging an absorber pattern so that the absorber pattern covers a position at which an actual phase defect occurs.SOLUTION: A method of manufacturing a reflection type mask, which reduces an influence of a phase defect, includes the steps of: grasping an amount of positional displacement between a surface defect position, which is detected through far ultraviolet light inspection of a reflection type mask blank, and an actual phase defect position in advance; detecting a surface defect and obtaining positional information by performing surface defect inspection on the reflection type mask blank using far ultraviolet light; calculating an actual phase defect position and range from the amount of positional displacement and the positional information of the surface defect; and arranging a pattern of an absorber layer on the basis of the calculated actual phase defect position and range.

Description

  The present invention is for EUV exposure for transferring a mask pattern onto a wafer using extreme ultraviolet light (Extreme Ultra Violet: hereinafter referred to as EUV) used for manufacturing high-density integrated circuits such as LSI and VLSI. The present invention relates to a method for manufacturing a reflective mask (hereinafter also simply referred to as a reflective mask), and more particularly to a method for manufacturing a reflective mask that reduces the influence of phase defects.

  Along with the miniaturization of semiconductor devices, an exposure method of transferring a pattern onto a wafer using a photomask is currently being performed by an optical projection exposure apparatus using an ArF excimer laser. In these exposure methods using an optical projection exposure apparatus, the resolution limit will eventually be reached. Therefore, new pattern forming methods such as direct drawing using an electron beam drawing apparatus, imprint lithography, and EUV lithography have been proposed.

  Among these new lithography techniques, EUV exposure is a technique in which EUV light having a wavelength shorter than that of an excimer laser and having a wavelength of about 13.5 nm is used, and the exposure is usually reduced to about 1/4. It is regarded as the limit of wavelength conversion, and is attracting attention as a lithography technique for semiconductor devices. In EUV exposure, since a refractive optical system cannot be used due to a short wavelength, a reflective optical system is used, and a reflective mask has been proposed as a mask.

  A reflective mask for EUV exposure has a structure including at least a substrate, a reflective layer that reflects EUV light in a multilayer structure provided on the substrate, and an absorber layer that absorbs EUV light provided on the reflective layer. This is a mask in which a pattern is formed by the absorber layer. The EUV light incident on the reflective mask is reflected by the reflective layer, absorbed by the absorber layer, and a reduced transfer pattern is formed on the wafer by the reflected EUV light.

One of the technical problems that must be solved for a reflective mask for EUV exposure is the problem of mask defects that greatly affect the transfer pattern. As a defect of the reflective mask, there is a pattern defect when a pattern on the mask that is originally necessary is missing or missing (referred to as a white defect), or when an unnecessary surplus pattern exists (referred to as a black defect). In addition, a phase defect of a multilayer reflective layer of a reflective mask is known as a defect peculiar to a reflective mask for EUV exposure that uses exposure light with a short wavelength. The present invention relates to a reflective mask manufacturing method for reducing the influence of this phase defect.
Next, phase defects in the multilayer reflective layer of the reflective mask will be described with reference to the drawings.

  FIG. 11 is a partial cross-sectional view of a reflective mask for EUV exposure including a phase defect portion provided with an absorber pattern 93 serving as a mask pattern. As shown in FIG. If a minute convex portion 95a exists on the surface of the substrate 91, or if a minute concave portion 95b exists on the surface of the mask substrate 91 as shown in FIG. 11B, it is schematically shown in the circle of FIG. As shown, the periodic structure of the multilayer reflective layer 92 formed on the substrate 91 is disturbed, and the reflected light undergoes a phase change due to the unevenness. This disorder of the periodic structure of the multilayer reflective layer 92 due to minute protrusions or recesses existing on the substrate 91 that changes the phase is called a phase defect. The phase defect causes a phase difference in EUV reflected light, degrades the optical profile on the wafer on which the pattern is transferred, and makes it difficult to resolve the pattern, or causes deterioration by changing the pattern dimension.

  When light having a short wavelength such as EUV light is used as exposure light, the phase change of the EUV reflected light through the multilayer reflective layer becomes very sensitive to the unevenness of the substrate surface as described above, so that the transferred image is transferred to the transfer image. In particular, when unevenness is present on the reflection surface near the pattern, a change in phase due to small unevenness cannot be ignored. For example, when EUV light having a wavelength of about 13.5 nm is used as exposure light, even a minute convex portion having a height of about 2 nm to 3 nm becomes a phase defect, and a dimensional error of a transferred fine LSI pattern cannot be allowed. End up.

  FIG. 8 is a schematic plan view of a reflective mask pattern including a phase defect. If there is a phase defect 83 in the reflective layer 81 between the absorber patterns 82 (pattern-extracted portion), the amount of light decreases due to the phase difference effect. This will affect the transfer. The phase defect is an important issue for a reflective mask for EUV exposure.

  Therefore, various methods have been proposed as a method for correcting the phase defect of the reflective mask. As a typical method for correcting a phase defect, as a first method, as shown in FIG. 9, a method of shifting a pattern by a distance L so that an absorber pattern 82 is covered on a phase defect 83 (pattern shift method and For example, as shown in FIG. 10, the second method is to mask the absorber pattern 82 adjacent to the phase defect 83 of the mask to reduce the amount of light due to the phase defect. Has been proposed (referred to as Patent Document 2, for example).

  The phase defect of the reflective mask has a convex or concave shape of several nanometers. At present, for inspection of the phase defect of the reflective mask, in general, the deep UV (Deep UV; wavelength 193 nm) in which the optical system is stable is used. Hereinafter, an inspection by a DUV inspection machine using light) will be performed. In the inspection using DUV light, the concave and convex shape of the reflective layer on the very surface of the mask is captured and the defect is detected.

  However, in recent research, the phase defect of the reflective mask blank grows obliquely from a defect that becomes a seed at the bottom of the multilayer reflective film (hereinafter referred to as a seed defect), and the phase defect vertically extends from the bottom of the reflective film. It was proved that they were not formed, and it became clear that there was a deviation between the position of the surface defect of the mask detected by the DUV inspection machine and the position of the actual phase defect (Non-Patent Document 1). reference).

JP 2010-219445 A JP-T 2002-532738

T.A. Amano et al. “Phase defect detection and analysis using actinic blank inspection tool and TEM”, 2011 EUV International Symposium on EUVL (Oct., 2011).

FIG. 3 is a diagram illustrating oblique growth of phase defects in the reflective layer, and FIG. 3A is a schematic cross-sectional view illustrating oblique growth of phase defects in the multilayer reflective film of the reflective mask blank 20. FIG. 3B is a schematic plan view showing the range of phase defects. When a multilayer reflective film 11 is laminated on a substrate (not shown) and a seed defect 13 that is a base of a surface defect exists on the substrate at the bottom of the reflective film 11, the reflective film 11 is laminated. Accompanying this, the phase defects grow obliquely upward, and form convex surface defects on the outermost surface of the reflective film 11. In the inspection by the DUV inspection machine, the defect range 14 in the surface shape is measured. However, in the EUV exposure, the multilayer reflective film 11 contributes to the reflection of EUV light not only on the surface layer but also on the lower layer. As shown in FIG. 3, due to the oblique growth of phase defects in the reflective film 11, the actual phase defect range 15 during EUV exposure is shifted from the surface defect range 14 by the DUV inspection machine. Become.
In the present invention, the actual phase defect means a defect that becomes a phase defect during EUV exposure, and the actual phase defect range means a range that becomes a phase defect during EUV exposure.

  4A and 4B are a schematic cross-sectional view (FIG. 4A) for explaining a conventional method for manufacturing a reflective mask for EUV exposure and a schematic plan view showing a range of phase defects (FIG. 4B). Conventionally, the phase defect was considered to be formed by vertically growing seed defects vertically, but as described above, the actual phase defect range 35 deviates from the surface defect range 34 by the DUV inspection machine. In the state where the absorber pattern 32 is arranged based on the defect position information of the DUV inspection machine and the phase defect is to be hidden under the absorber pattern 32, the actual phase defect 35 is obtained as shown in FIG. However, it has protruded from the absorber pattern 32, and a problem has arisen that the range of influence of the actual phase defect 32 cannot be sufficiently covered.

  Therefore, the present invention has been made in view of solving the above problems. That is, it is an object of the present invention to accurately grasp the position of a phase defect that grows obliquely from a seed defect in a manufacturing method of a reflective mask for EUV exposure that reduces the influence of the phase defect, and absorbs the absorber in the actual phase defect range. An object of the present invention is to provide a method for manufacturing a reflective mask for EUV exposure, which is arranged so as to cover a pattern and can obtain a good mask pattern transfer.

  In order to solve the above problems, a reflective mask manufacturing method for reducing the influence of a phase defect according to the first aspect of the present invention includes a substrate and a reflective layer that reflects EUV light on the substrate. And a reflective mask blank for EUV exposure in which at least the absorber layer that absorbs the EUV light is provided on the reflective layer, and a method of manufacturing a reflective mask that reduces the influence of phase defects, 1) a step of grasping in advance the amount of positional deviation between the position of the surface defect detected by inspection of the reflective mask blank with far ultraviolet light and the position of the actual phase defect; and (2) the far ultraviolet light. The step of inspecting the surface defect of the reflective mask blank to obtain the surface defect detection and position information, and (3) the actual phase from the positional deviation amount and the position information of the surface defect of the reflective mask blank. Flawed Calculating a location and range and is characterized in that it comprises the steps of disposing a pattern of (4) the absorber layer based on the position and range of the actual phase defects the calculated.

  According to a second aspect of the present invention, there is provided a reflective mask manufacturing method for reducing the influence of a phase defect. In the reflective mask manufacturing method according to the first aspect, in the step (1), the position is determined. In grasping the amount of displacement in advance, the amount of displacement is measured with a transmission electron microscope using a mask blank of the same lot as the reflective mask blank.

  According to a third aspect of the present invention, there is provided a reflective mask manufacturing method for reducing the influence of phase defects according to the first aspect of the present invention, in the reflective mask manufacturing method according to the first aspect, in the step (1). In grasping the amount of deviation in advance, a pre-programmed phase defect is provided on the substrate, and a substrate on which at least the reflective layer is formed so as to cover the phase defect is produced, and the programmed phase defect is used using the substrate. The amount of positional deviation between the position of the surface and the position of the surface defect is measured.

  According to a fourth aspect of the present invention, there is provided a reflective mask manufacturing method for reducing the influence of a phase defect. The reflective mask manufacturing method according to the third aspect, wherein the substrate on which the reflective layer is formed is The substrate has an alignment mark, and the positional deviation is measured based on the alignment mark.

  The reflective mask manufacturing method for reducing the influence of the phase defect according to the fifth aspect of the present invention is the reflective mask manufacturing method according to any one of the first to fourth aspects. The positional deviation amount is expressed as a function of the distance from the center of the mask blank of the surface defect of the reflective mask blank and the angle at which the actual phase defect grows.

  According to the reflective mask manufacturing method for reducing the influence of the phase defect of the present invention, the absorber pattern is accurately arranged at the phase defect position based on the information of the reflective mask blank defect inspection by the DUV inspection machine, and the wafer The influence of phase defects on the transfer can be reduced, and a high-quality reflective mask can be manufactured.

It is a process flow figure of the manufacturing method of the reflective mask for EUV exposure which reduces the influence of the phase defect of this invention. It is the cross-sectional schematic diagram and plane schematic diagram explaining the manufacturing method of the reflective mask for EUV exposure which reduces the influence of the phase defect of this invention. It is the cross-sectional schematic diagram and plane schematic diagram explaining the diagonal growth of the phase defect in a reflection layer. It is the cross-sectional schematic diagram and plane schematic diagram explaining the manufacturing method of the conventional reflective mask for EUV exposure. In this invention, it is a process cross-sectional schematic diagram which shows the method of etching a board | substrate and providing the alignment mark of a recessed part. In this invention, it is a process cross-sectional schematic diagram which shows the method of providing the alignment mark of a convex part on a board | substrate. It is a graph which shows the relationship between the distance from the mask blank center of a phase defect, and the growth angle of a defect. It is a partial plane schematic diagram of the reflective mask which has a phase defect. It is a plane schematic diagram explaining the conventional correction method (pattern shift method) of the phase defect of a reflective mask. It is a plane schematic diagram explaining the other conventional correction method (defective part pattern correction method) of the phase defect of a reflective mask. It is a partial cross-section schematic diagram of the reflective mask containing a phase defect.

(Reflective mask manufacturing method)
Hereinafter, an embodiment of a reflective mask manufacturing method of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a process flow diagram of a reflective mask manufacturing method for reducing the influence of phase defects according to the present invention. This will be described with reference to FIG.

  First, a reflective mask blank for EUV exposure is prepared, which includes at least a substrate, a multilayer reflective layer that reflects EUV light on the substrate, and an absorber layer that absorbs EUV light on the reflective layer (S1). ).

In addition to the reflective layer and the absorber layer, the thin film layer constituting the reflective mask blank for performing the reflective mask manufacturing method of the present invention has an absorber layer used for etching the absorber layer. In order to increase the sensitivity at the optical inspection of the hard mask layer provided, the capping layer provided on the reflective layer as a protective film during oxidation prevention and mask cleaning, the buffer layer to prevent etching damage to the reflective layer, and the mask pattern Further, a low reflection layer provided on the absorber layer and a thin film layer such as a conductive layer provided on the back surface of the substrate for an electrostatic chuck when the mask is installed in the exposure apparatus may be provided.
In the following description of the manufacturing process, a case of a reflective mask blank provided with a multilayer reflective layer and an absorber layer will be described as an example.

  Next, the position of the surface defect detected by the inspection by the DUV inspection machine (wavelength 193 nm) of the reflective mask blank, and the phase defect (actually due to the seed defect existing at the bottom of the multilayer reflective layer that is the basis of this surface defect) The amount of positional deviation from the position of (phase defect) is grasped in advance (S2).

  Next, the surface defect of the reflective mask blank actually used for manufacturing the reflective mask is detected by the DUV inspection machine, and the position of the surface defect is measured to obtain position information (S3).

  Next, the actual position and range of the phase defect are calculated from the positional deviation amount and the surface defect position information ascertained in advance (S4).

  Based on the calculated phase defect range, in order to reduce the influence of the phase defect, the arrangement of the absorber pattern is determined so as to cover the phase defect with the absorber pattern (S5).

  Next, on the absorber layer, an electron beam resist for forming an absorber pattern serving as a transfer pattern for the transfer target is applied, and a pattern is drawn with an electron beam based on the arrangement of the absorber pattern and developed. Then, a resist pattern is formed (S6).

  Next, the absorber layer is dry-etched based on the resist pattern, the resist pattern is peeled off to form the absorber pattern (S7), and the actual phase defect is covered with the absorber pattern to reduce the influence of the phase defect. A reflection type mask is prepared (S8).

  2A and 2B are a schematic cross-sectional view (FIG. 2A) illustrating a method for manufacturing a reflective mask for EUV exposure that reduces the influence of the phase defect of the present invention, and a schematic plan view illustrating a phase defect range (FIG. 2B). )). In the case where a multilayer reflective film 11 is laminated on a substrate (not shown) of the reflective mask blank 10 and a seed defect 13 is present on the substrate at the bottom of the reflective film 11, the reflective film 11 is laminated. Accordingly, the phase defect grows obliquely upward, and forms a convex portion on the outermost surface of the reflective film 11. In the inspection by the DUV inspection machine, the defect range 14 in the surface shape is measured. However, due to the oblique growth of phase defects in the reflective film 11, the actual phase defect range 15 during EUV exposure is shifted from the surface defect range 14 by the DUV inspection machine.

  As described above, the position and range 15 of the actual phase defect are calculated from the positional deviation amount and the position information of the surface defect of the reflective mask blank, and are absorbed based on the calculated position and range of the actual phase defect. By disposing the body pattern 12, it is possible to manufacture a reflective mask for EUV exposure with reduced influence of phase defects.

  In the step (S2) of the reflective mask manufacturing method of the present invention described above, when grasping the positional deviation amount in advance, using a mask blank of the same lot as the reflective mask blank used for manufacturing the reflective mask, A method of measuring the amount of misalignment with a transmission electron microscope can be used. This is because by using a transmission electron microscope, it is possible to simultaneously capture the surface defects and the seed defects present at the bottom of the multilayer reflective layer in the field of view, and clearly grasp the range of the phase defects. When a plurality of reflective mask blanks are manufactured under the same conditions by the same manufacturing apparatus, the positional deviation amounts of the phase defects of the mask blanks can be handled as the same value.

  Further, in the above step (S2), another method can be used for grasping the amount of displacement in advance. In this method, a substrate provided with a pre-programmed phase defect is manufactured, the amount of misalignment between the position of the programmed phase defect and the position of the surface defect is measured, and the misalignment amount is grasped in advance. In the case of this method, in view of the fact that the oblique growth of phase defects originates from the reflective layer, a substrate on which at least the reflective layer is formed is used. Of course, an absorber layer may be provided on the reflective layer. Since the position of the seed defect of the programmed phase defect (seed defect) is known, the amount of misalignment can be determined in advance only by measuring the surface defect without using a transmission electron microscope for destructive inspection of the mask blank used for measurement. There is an advantage that it becomes possible to grasp.

  The method using a substrate provided with the above-described programmed phase defect (seed defect) is such that the programmed seed defect is fine, and the electron beam drawing position and the reflective layer are simply set for accuracy such as the magnification of the apparatus used. It is not easy to compare the displacement of defect positions after film formation. Therefore, it is preferable to prepare an alignment mark on the substrate in advance and perform pattern drawing and inspection with an electron beam based on this mark. In forming the reflective layer, the alignment mark also grows obliquely. Therefore, the inspection after the reflective layer is formed needs to be performed by removing the reflective layer in the alignment mark portion.

  5 and 6 are process cross-sectional schematic diagrams showing two methods of forming alignment marks on a substrate in a reflective mask manufacturing method for reducing the influence of phase defects according to the present invention. FIG. 6 is a process cross-sectional schematic diagram showing a method of providing a concave alignment mark by etching the substrate, and FIG. 6 is a process cross-sectional schematic diagram showing a method of providing a convex alignment mark on the substrate. Hereinafter, a method for providing alignment marks will be described in more detail with reference to the drawings.

(First method of forming alignment marks on the substrate)
The first method is a method in which the substrate is etched to provide concave alignment marks.
First, a resist pattern is formed on a substrate such as a quartz glass substrate by an electron beam lithography technique, and the substrate is etched to provide concave alignment marks 52 on the substrate 51 as shown in FIG.

  Next, in order to form a pre-programmed phase defect on the substrate 51, a thin film layer of a metal or a metal compound is formed, a resist pattern is formed by an electron beam lithography technique based on the alignment mark 52, and the above-mentioned The thin film layer is etched to provide phase defects (seed defects) 53 on the substrate 51 as shown in FIG. In the present invention, the programmed phase defect means an intentionally provided seed defect having a predetermined size and height at a predetermined position on the substrate. The number, size, and height of the programmed phase defects can be set arbitrarily. In FIG. 5B, the seed defects 53 are shown to have the same shape and height, but they may not be the same.

  Next, as shown in FIG. 5C, a reflective layer 54 is formed on the substrate 51 to a predetermined thickness so as to cover the phase defect (seed defect) 53. For example, a reflective layer made of a multilayer film in which 40 layers each of 2.74 nm thick Mo and 4.11 nm thick Si are stacked. A convex surface defect 55 based on the seed defect 53 is generated on the surface of the reflective layer 54 and grows obliquely from the position of the seed defect 53. Further, FIG. 5C shows that the reflective layer 54 on the alignment mark 52 also grows obliquely.

  Next, the reflective layer 54 in the portion of the alignment mark 52 that is obliquely grown is removed, and the concave alignment mark 52 is exposed on the substrate 51 in the reflective layer removal region 56, as shown in FIG.

  Next, based on the alignment mark 52 in the recess, the amount of positional deviation between the position of the programmed phase defect (seed defect) 53 and the position of the surface defect 55 detected by the DUV inspection machine is measured, and the amount of positional deviation is measured. Know in advance.

(Second method of forming alignment marks on the substrate)
The second method is a method of providing a convex alignment mark on a substrate.
First, in order to form pre-programmed phase defects and alignment marks on a substrate such as a quartz glass substrate, a thin film layer of metal or metal compound is formed, a resist pattern is formed by electron beam lithography technology, and the above thin film The layer is etched to form alignment marks 62 and phase defects (seed defects) 63 on the substrate 61 as shown in FIG.

  Next, as shown in FIG. 6B, a reflective layer 64 is formed to a predetermined thickness on the substrate 61 so as to cover the alignment mark 62 and the phase defect (seed defect) 63. For example, the reflective layer 64 made of a multilayer film in which 40 layers each of 2.74 nm thick Mo and 4.11 nm thick Si are provided. A convex surface defect 65 based on the seed defect 63 is generated on the surface of the reflective layer 64 and grows obliquely from the position of the seed defect 63. Further, it is shown that the reflective layer 64 on the alignment mark 62 also grows obliquely.

  Next, the reflective layer 64 in the portion of the alignment mark 62 growing obliquely is removed, and the convex alignment mark 62 is exposed on the substrate 61 in the reflective layer removal region 66 as shown in FIG.

  Next, based on the alignment mark 62 on the convex portion, the amount of positional deviation between the position of the programmed phase defect (seed defect) 63 and the position of the surface defect 65 detected by the DUV inspection machine is measured, and the amount of positional deviation is measured. Know in advance.

  In the present invention, in both the first method and the second method described above, a phase defect (seed defect) is inspected after a programmed phase defect (seed defect) is produced in order to reduce errors between different apparatuses. It is preferable to detect the defect position and compare this result with the inspection after film formation.

  In the method of providing the programmed phase defect (seed defect), the material of the metal or metal compound thin film layer used as the seed defect is not particularly limited, and examples thereof include chromium and a chromium compound. .

  As an example of an embodiment of the present invention, the present inventor examines the position of an actual phase defect of a reflective mask blank and the amount of positional deviation of a phase defect (surface defect) detected by a DUV inspection machine (wavelength 193 nm). As a result, it was found that the distribution has a substantially concentric distribution, and phase defects grow from the center of the reflective mask blank to the outside and obliquely upward and outward. FIG. 7 shows the relationship between the distance (mm) from the center of the reflective mask blank and the actual phase defect growth angle (degrees). The amount of deviation between the position of the seed defect and the actual phase defect and the position of the surface defect detected by the DUV inspection machine was measured using a transmission electron microscope.

As shown in FIG. 7, the deviation amount and direction between the defect position by the DUV inspection and the actual phase defect position are expressed as a function of the distance from the center of the reflective mask blank and the angle at which the actual phase defect grows. Can do. For example, in the case shown in FIG. 7, the function shows a curve close to a parabola with the center of the reflective mask blank as the apex, and the deviation distribution is almost concentric.
Next, the reflective mask blank used for the reflective mask manufacturing method of the present invention will be described.

(Reflective mask blank)
A reflective mask blank used in the method for producing a reflective mask of the present invention is a mask provided with at least a substrate, a reflective layer that reflects EUV light on the substrate, and an absorber layer that absorbs EUV light on the reflective layer. Although it is a blank, other thin film layers may be provided on the function of the mask. The desirable form of each material which comprises the reflective mask blank used for the manufacturing method of the reflective mask of this invention is demonstrated below.

(substrate)
The substrate used for the reflective mask blank has a low coefficient of thermal expansion in order to maintain high pattern position accuracy, and has high smoothness and flatness to obtain high reflectivity and transfer accuracy. A glass substrate such as synthetic quartz glass, SiO ₂ —TiO ₂ low thermal expansion glass, or crystallized glass on which β quartz solid solution is deposited can be used.

(Reflective layer)
The multilayer reflective layer is made of a material that reflects EUV light (typically about 13.5 nm in wavelength) used for EUV exposure with a high reflectance, and a multilayer film made of molybdenum (Mo) and silicon (Si) is often used. For example, a reflective layer made of a multilayer film in which 40 layers each of 2.74 nm thick Mo and 4.11 nm thick Si are stacked. In the case of a multilayer film made of Mo and Si, an Si film is first formed in an Ar gas atmosphere using an Si target by ion beam sputtering, and then an Mo film is used in an Ar gas atmosphere using an Mo target. A multi-layered reflective layer is obtained by stacking 30 to 60 cycles, preferably 40 cycles, with this as one cycle.

(Capping layer)
In order to increase the reflectivity of the multilayer reflective layer, it is preferable to use Mo having a large refractive index as the uppermost layer. However, since Mo is easily oxidized in the atmosphere and the reflectivity is lowered, it prevents oxidation and protection during mask cleaning. For this purpose, it is preferable to form a capping layer by depositing Si or ruthenium (Ru) by sputtering or the like. For example, Si as a capping layer is provided in a thickness of 11 nm on the uppermost layer of the reflective layer. When Ru is used as a capping layer, Ru also functions as a buffer layer to be described later, so that the buffer layer can be omitted.

(Buffer layer)
When a pattern is formed by dry etching an absorber layer that absorbs EUV light, in order to prevent damage to the lower reflective layer and capping layer due to dry etching, the reflective layer and the absorber layer are usually A buffer layer is provided therebetween. As a material for the buffer layer, thin films such as SiO ₂ , Al ₂ O ₃ , Cr, and CrN are used, and chromium nitride (CrN) is more preferable. The CrN film has high etching resistance when, for example, a tantalum nitride (TaN) film is used for the absorber layer and dry-etched with chlorine gas, and the material of the buffer layer and the material of the hard mask layer described later are the same material. This is because etching can be performed simultaneously, and the mask manufacturing process is shortened. For example, when forming a CrN film, it is preferable to form a film with a film thickness in the range of about 5 nm to 20 nm in a mixed gas atmosphere of argon (Ar) and nitrogen using a Cr target by a DC magnetron sputtering method. .

(Absorber layer)
The material of the absorber layer 23a that forms a mask pattern and absorbs EUV light is mainly Ta such as tantalum (Ta), tantalum nitride (TaN), tantalum boride (TaB), tantalum boride (TaBN). The material used as a component is used in a film thickness range of about 35 nm to 60 nm, more preferably in a range of 40 nm to 55 nm. However, the above thickness is an example when CrN is used as the buffer layer with a thickness of 10 nm. When the material and thickness of the buffer layer are changed, it is necessary to adjust the thickness of the absorber layer according to the buffer layer. There is. For example, when the buffer layer has a CrN thickness of 20 nm, it is necessary to reduce the thickness of the absorber layer by about 10 nm.

(Low reflective layer)
When the mask pattern is optically inspected on the absorber layer, a low reflection layer that is low in reflection with respect to inspection light (199 nm or 257 nm) is often provided. Examples of the material of the low reflection layer include tantalum compounds containing oxygen such as tantalum oxide (TaO), oxynitride (TaNO), boron oxide (TaBO), and boron oxynitride (TaBNO), and silicon oxide ( (SiO _x ), chromium nitride (CrN), and the like. The film thickness is in the range of about 5 nm to 30 nm, and more preferably in the range of about 10 nm to 20 nm. The hard mask layer described below can also serve as the low reflection layer.

(Hard mask layer)
A hard mask layer used for etching the absorber layer may be provided on the absorber layer of the reflective mask blank. The hard mask layer needs to have an etching resistance that allows a sufficient selection ratio between the absorption layer and the etching, and can be easily removed after the etching is completed, and also increases the detection sensitivity during optical inspection of the mask pattern. Therefore, it is more preferable to serve as a low reflection layer for inspection because the film formation and etching steps are shortened. Examples of the material of the hard mask layer include tantalum compounds containing oxygen, such as tantalum oxide (TaO), tantalum oxynitride (TaNO), tantalum boride (TaBO), and tantalum oxynitride (TaBNO), or chromium ( Cr and Cr-based compounds such as Cr), chromium oxide (CrO), chromium nitride (CrN), chromium oxynitride (CrNO), or silicon oxynitride (SiON) are used in a thickness range of about 10 nm. The chromium-based material is a preferable material because it has a strong resistance to a fluorine-based gas or chlorine gas plasma used for dry etching of an oxygen-containing tantalum compound, and is easily wet-etched.

(Conductive layer)
In many cases, a conductive layer is provided on the substrate surface opposite to the pattern side of the reflective mask blank for EUV exposure for an electrostatic chuck when the mask is placed in an exposure apparatus. As a material of the conductive layer, a thin film such as a metal or metal nitride showing conductivity is provided. For example, chromium (Cr), chromium nitride (CrN), or the like is formed to a thickness of about 20 nm to 150 nm. Used. When the hard mask layer is composed of a chromium-based material, the conductive layer needs to be made of a material that is not etched during wet etching of the chromium-based material, such as tantalum nitride (TaN).
Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
In the following procedure, a plurality of reflective mask blanks were produced using the same apparatus under the same conditions.
On a main surface of a 6-inch square (0.25-inch thick) synthetic quartz substrate that has been optically polished, an Si film is formed to 4.2 nm using an Si target in an Ar gas atmosphere by ion beam sputtering. Next, a Mo film is formed to 2.8 nm using a Mo target, and this is set as one period to form a multilayer reflective layer, and a ruthenium (Ru) film is formed to 2.5 nm thereon. Thus, a capping layer was obtained. The Ru film also serves as a buffer layer.

  Subsequently, a TaN film having a thickness of 40 nm is formed on the above Ru film by DC magnetron sputtering using a Ta target in a mixed gas atmosphere of Ar and nitrogen, and then mixed with Ar and oxygen. A TaO film having a thickness of 10 nm was formed in a gas atmosphere to obtain an absorber layer that absorbs EUV light. The TaO film also serves as a low reflection layer at the time of optical inspection. On the other hand, a TaN film having a thickness of 30 nm was formed on the other main surface of the substrate to form a conductive layer, and a reflective mask blank for EUV exposure was obtained.

  Next, using a mask blank of the same lot as the reflective mask blank used for the production of the reflective mask, the position of the surface defect detected by the inspection of the reflective mask blank by the DUV inspection machine (wavelength 193 nm), and this The position deviation amount between the position of the phase defect (seed defect) existing at the bottom of the multilayer reflective layer that is the basis of the surface defect and the range of the actual phase defect was grasped in advance.

  The amount and direction of deviation between the defect position by the DUV inspection and the actual phase defect position can be a function of the position from the center of the reflective mask blank. As shown in FIG. A curve close to a parabola with the center of the mold mask blank as the apex was shown, and the distribution of the shift amount was almost concentric. The amount of deviation between the position of the seed defect and the actual phase defect and the position of the surface defect detected by the DUV inspection machine was measured using a transmission electron microscope.

  Next, the surface defect of the surface of the TaO film of the reflective mask blank was examined using a surface defect inspection apparatus by DUV having a wavelength of 193 nm, and recorded as position information of the surface defect. The size of the surface defect was a maximum width of 140 nm and a height of 3 nm.

  Next, the position coordinates of the actual phase defect and the range of influence of the phase defect were calculated from the positional deviation amount and the position information of the surface defect of the reflective mask blank.

  Based on the above calculation result, in order to reduce the influence of the phase defect, the arrangement of the absorber pattern was determined so as to cover the phase defect with the absorber pattern.

  Next, using this reflective mask blank, an electron beam resist is applied to the TaO film with a film thickness of 100 nm, the pattern of the absorber pattern is drawn with an electron beam drawing apparatus, developed, and transferred to a pattern on the wafer. A resist pattern having a corresponding pattern was formed.

  Next, using the resist pattern as a mask, the TaO film is dry-etched with fluorine gas, and then the absorber layer TaN film is dry-etched with chlorine gas to form an absorber pattern, thereby producing a reflective mask for EUV exposure. did.

  When the resist on the wafer was subjected to pattern exposure using the above-described reflective mask, a good resist pattern not affected by phase defects was obtained.

(Example 2)
In order to form alignment marks on the synthetic quartz substrate, chromium was sputtered to a thickness of 5 nm to form a chromium thin film layer. Next, an electron beam resist is applied, a resist pattern of alignment marks is formed by electron beam drawing, chromium is etched using a mixed gas of chlorine and oxygen using the resist pattern as a mask, and then the resist pattern is etched with oxygen plasma. After peeling, the quartz substrate was etched with CF4 gas using the chromium pattern as a mask, and an alignment mark of a recess having a depth of 100 nm was provided on the quartz substrate.

  Next, a chromium nitride film is formed to a thickness of 5 nm for the programmed phase defect on the substrate provided with the alignment mark, and a resist pattern for the phase defect is formed by electron beam drawing using the alignment mark as a reference. The chromium film was etched to provide a plurality of programmed phase defects (seed defects) on the substrate. At the stage where the programmed phase defect (seed defect) was produced, the phase defect (seed defect) was inspected, and the position of the phase defect was detected and confirmed again.

  Next, covering the phase defects (seed defects), the Si film was formed to 4.2 nm by the ion beam sputtering method in the same manner as in Example 1, and then the Mo film was formed to 2.8 nm. A multilayer reflection layer was formed by laminating 40 periods as one period. Next, an electron beam resist is applied on the reflective layer, electron beam drawing and development are performed to expose the reflective layer in the alignment mark portion, the reflective layer in the peripheral area of the alignment mark is removed by etching, and the concave portion is aligned on the substrate. The mark was exposed.

  Next, with reference to the alignment mark in the recess, the amount of positional deviation between the position of the programmed phase defect (seed defect) and the position of the surface defect detected by the DUV inspection machine was measured, and the amount of positional deviation was grasped in advance. .

  Next, using the same reflective mask blank as in Example 1, the surface of the film was examined using a DUV inspection machine having a wavelength of 193 nm, and recorded as position information of the surface defect.

  Next, the position coordinates of the actual phase defect of the reflective mask blank and the influence range of the phase defect were calculated from the positional deviation amount and the position information of the surface defect of the reflective mask blank.

  Based on the above calculation result, in order to reduce the influence of the phase defect, the arrangement of the absorber pattern was determined so as to cover the phase defect with the absorber pattern.

  Next, using this reflective mask blank, an electron beam resist is applied, an absorber pattern is drawn with an electron beam drawing apparatus, developed, and a resist pattern having a pattern corresponding to the pattern to be transferred onto the wafer Formed.

  Next, using the resist pattern as a mask, the TaN film of the absorber layer was dry-etched with chlorine gas to form an absorber pattern, and a reflective mask for EUV exposure was produced.

  When the resist on the wafer was subjected to pattern exposure using the above-described reflective mask, a good resist pattern not affected by phase defects was obtained.

DESCRIPTION OF SYMBOLS 10 Reflective mask 11 Reflective layer 12 Absorber pattern 13 Seed defect 14 Surface defect range 15 Actual phase defect range 16 Seed defect range 20 Reflective mask blank 30 Reflective mask 31 Reflective layer 32 Absorber pattern 33 Seed defect 34 Defect range in surface shape 35 Actual phase defect range 36 Seed defect range 51, 61 Substrate 52, 62 Alignment mark 53, 63 Programmed phase defect (seed defect)
54, 64 Reflective layer 55, 65 Phase defect (surface defect)
56, 66 Reflection layer removal region 81 Reflection layer 82 Absorber pattern 83 Phase defect 91 Substrate 92 Reflection layer 93 Absorber pattern 95a Convex part 95b Concave part 96a Phase defect 96b Phase defect

Claims (5)

Use of a reflective mask blank for EUV exposure comprising at least a substrate, a reflective layer for reflecting EUV light on the substrate, and an absorber layer for absorbing EUV light on the reflective layer, and the influence of phase defects A reflective mask manufacturing method for reducing
(1) a step of grasping in advance the amount of positional deviation between the position of the surface defect detected by the far-ultraviolet light inspection of the reflective mask blank and the position of the actual phase defect;
(2) Inspecting the surface defect of the reflective mask blank with the far ultraviolet light to detect the surface defect and obtain position information;
(3) calculating the position and range of the actual phase defect from the positional deviation amount and the position information of the surface defect of the reflective mask blank;
(4) Arranging the pattern of the absorber layer based on the calculated position and range of the actual phase defect;
A reflective mask manufacturing method that reduces the influence of phase defects.   In the step (1), when the amount of misalignment is grasped in advance, the misregistration amount is measured by a transmission electron microscope using a mask blank of the same lot as the reflective mask blank. The manufacturing method of the reflection type mask which reduces the influence of the phase defect of Claim 1.   In the step (1), when grasping the positional deviation amount in advance, a preliminarily programmed phase defect is provided on the substrate, and a substrate on which at least the reflective layer is formed to cover the phase defect is manufactured, 2. The method of manufacturing a reflective mask for reducing an influence of a phase defect according to claim 1, wherein a positional deviation amount between the position of the programmed phase defect and the position of the surface defect is measured using a substrate.   4. The influence of the phase defect according to claim 3, wherein the substrate on which the reflective layer is formed has an alignment mark on the substrate, and the displacement amount is measured based on the alignment mark. A method of manufacturing a reflective mask to reduce.   2. The position shift amount is expressed as a function of a distance from a center of a mask blank of a surface defect of the reflective mask blank and an angle at which the actual phase defect grows. 5. A method for manufacturing a reflective mask that reduces the influence of the phase defect according to any one of items 1 to 4.

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