JP2012124196A - Method of manufacturing reflection-type phase shift mask for euv light exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of producing an alignment mark easily, having a high position accuracy of a pattern and a high quality, and suppressing manufacturing cost without reducing a reflection rate of exposure light, in a method of manufacturing a Levenson-type reflection-type phase shift mask having an alignment mark.SOLUTION: A method includes the following steps of: etching a substrate to provide an alignment mark consisting of a recessed part or a convex part of a substrate at a predetermined position before forming a multilayer reflection film on the substrate; and providing a recessed or convex step region for phase shifting means at a predetermined position on the substrate using the alignment mark as a reference. The recessed or convex step is set so that a phase difference between reflection light reflected from the multilayer reflection film surface of the step region and reflection light reflected from the multilayer reflection film surface on which no step region is provided becomes 180 degrees.

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. In particular, the present invention relates to a method for manufacturing a Levenson-type reflective phase shift mask.

  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, so a new pattern forming method such as a direct drawing technique using an electron beam drawing apparatus, an imprint lithography technique, or an EUV exposure technique has been proposed. .

  Among these new lithography techniques, the EUV exposure technique is a technique in which EUV light having a wavelength shorter than that of an excimer laser is about 13.5 nm, and the exposure is usually reduced to about 1/4. It is regarded as the limit of shortening the wavelength, 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.

  The reflective mask for EUV exposure includes at least a substrate, a reflective layer that reflects EUV light with a multilayer structure provided on the substrate, and an absorber layer that absorbs EUV light provided on the reflective layer. The mask 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.

  In the EUV exposure technology, in order to further improve the pattern transfer resolution by EUV exposure, the principle of the phase shift mask used in conventional ultraviolet and excimer laser exposure is changed to EUV exposure using a reflective optical system. Development is also underway. As a reflection type phase shift mask, proposals have been made to locally change the phase of exposure light and improve the resolving power by using interference between light whose phase has been changed and light whose phase has not changed.

  The Levenson-type reflective phase shift mask that locally changes the phase of the exposure light by 180 degrees can be expected to have a higher resolution than the reflective phase shift mask, and several proposals have been made.

  For example, FIG. 6 shows a first example of a Levenson-type reflection type phase shift mask, which can be called a reflection film laminated type, and has a structure that can be said to be a reflection film laminated type. (1) and the first protective film 2- (1) are formed, and the second multilayer film 1- (2) and the second protective film 2- (2), which become another highly reflective portion, are formed thereon. And a reflective phase shift mask of a reflective film stack type in which a pattern made of the intermediate film 3 formed between the first protective film and the second multilayer film is formed, and the thickness of the intermediate film 3 is high This is a mask having a thickness at which the reflectance of a reflective portion and another highly reflective portion are substantially equal and the phase difference is 180 degrees (see Patent Document 1).

  FIG. 7 shows a second example of the Levenson-type reflective phase shift mask, which can be said to be a reflective film digging type, where the multilayer reflective film on the substrate is locally h = λ / 4 (1− It is a reflective phase digging type reflective phase shift mask that etches to a depth of n). n is the average refractive index of the multilayer film, h is the etching depth of the multilayer film, and λ is the wavelength of the exposure light (see Patent Document 2).

JP 2006-179553 A US6875543 B2

  However, the reflective layer stack type reflective phase shift mask described in Patent Document 1 requires two reflective films made of several tens of thin films, so that the structure of the mask blank becomes very complicated. There are problems in that the number of steps during fabrication increases, mask manufacturing costs increase, and manufacturing yield decreases. Furthermore, since the intermediate film absorbs exposure light, there is a problem that not only the EUV light reflectivity is greatly reduced and the mask quality is lowered, but also the throughput during EUV exposure is greatly reduced. . In addition, there is a problem that it is difficult to accurately align the first multilayer film and the second multilayer film formed in a pattern.

  In addition, the reflective film digging-type reflective phase shift mask as described in Patent Document 2 has a large damage to the lower multilayer film in the etching process of the multilayer reflective film, and the EUV light reflectance is greatly reduced. There was a problem that could cause. Furthermore, EUV light is not reflected only on the surface of the multilayer film, but is reflected by multiple reflections from the inside of the multilayer film (approximately 31 layers of multilayer film), so that the surface is etched by 180 °. However, there is a problem that only a part of the reflected light can obtain the phase shift, and the improvement of the pattern resolving power due to the phase shift cannot be expected. In addition, since there is no etching stopper layer, it is difficult to control the depth during etching of the reflective film, and it is difficult to obtain a high-quality Levenson-type reflective phase shift mask. In addition, there is a problem that it is difficult to accurately align the digging position when etching the reflective film.

  By the way, in the Levenson-type reflective phase shift mask, when a resist pattern is formed by electron beam drawing, alignment is necessary for alignment between the main pattern and the shifter pattern having a phase difference of 180 degrees. Usually, the position of the secondary electron image of the alignment mark is detected using an electron beam. In the reflection type phase shift mask described in Patent Document 1 and Patent Document 2 described above, an alignment mark is created by stacking multiple reflective films or etching the reflective film. However, the process is complicated and the multilayer reflective film is easily damaged, and as a result, there is a limit to the improvement of the position accuracy and resolution of the mask pattern. Furthermore, since mark detection is performed through the resist layer, stable alignment marks cannot be detected, and inconveniences such as variations in alignment accuracy due to variations in the resist film are likely to occur.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is to provide an easy-to-create alignment mark in a highly accurate Levenson-type reflective phase shift mask manufacturing method in which an alignment mark is provided on a multilayer substrate and a phase shift is applied to all reflected light. To provide a manufacturing method of a reflective phase shift mask that does not damage the multilayer reflective film, does not decrease the reflectivity of exposure light, has high pattern position accuracy, and has high manufacturing cost. It is.

  In order to solve the above-mentioned problems, a manufacturing method of a reflective phase shift mask for EUV exposure according to claim 1 of the present invention includes a substrate and a multilayer that reflects EUV light formed on the substrate. A reflective film; and an absorber layer that absorbs EUV light formed on the multilayer reflective film, and the absorber layer partially removes the absorber layer to form a transfer pattern for a transfer target. A method of manufacturing a reflective phase shift mask for EUV exposure having an area where an absorber pattern is formed, wherein a first resist is formed on the substrate by electron beam drawing before forming the multilayer reflective film on the substrate. Forming a pattern, etching the substrate to provide an alignment mark made of a concave portion or a convex portion of the substrate at a predetermined position, and drawing the second by electron beam drawing based on the alignment mark Including a step of forming a step pattern of a concave portion or a convex portion for a phase shift means at a predetermined position of the substrate, and the reflected light of the EUV light reflected from the multilayer reflective film surface of the step region The step of the concave portion or the convex portion is set so as to produce a phase difference of 180 degrees with the reflected light reflected from the surface of the multilayer reflective film not provided with the step region.

  According to the manufacturing method of the reflective phase shift mask for EUV exposure according to the first aspect of the present invention, the step region of the concave portion or the convex portion for the phase shift means is provided at a predetermined position of the substrate. Because of this, the inside of the multilayer reflective film formed on the substrate also has a phase shift effect, and the high precision that gave the phase shift effect to all EUV reflected light including not only the surface of the multilayer reflective film but also the inside A Levenson-type reflective phase shift mask can be realized. In the present invention, it is not necessary to change the number of layers of the multilayer reflective film, and the multilayer reflective film is not subjected to pattern etching, so that the multilayer reflective film is not damaged and a high quality mask can be obtained. The position of the concave portion or the convex portion for the phase shift means can be accurately positioned by reading the alignment mark first provided on the substrate.

  The manufacturing method of a reflective phase shift mask for EUV exposure according to claim 2 of the present invention is the method of manufacturing a reflective phase shift mask for EUV exposure according to claim 1, wherein electron beam drawing is performed on the substrate. In the step of forming the first resist pattern, a hard mask layer is formed on the substrate, a first resist layer is formed, the first resist layer is drawn with an electron beam, and an alignment mark is formed. Forming the first resist pattern, etching the hard mask layer using the first resist pattern as a mask to form a hard mask pattern for an alignment mark, and then peeling the first resist pattern; The substrate is etched using the hard mask pattern for the alignment mark as a mask, and a concave portion of the substrate or And it is characterized in providing an alignment mark made of parts.

  According to the method of manufacturing a reflective phase shift mask for EUV exposure according to the second aspect of the present invention, when the substrate is etched to provide a concave portion or a convex portion of the substrate at a predetermined position, the resist pattern alone is not resistant to etching. When the property is insufficient, it is preferable to perform the process according to claim 1 after forming a hard mask layer on the substrate. Generation of pattern defects due to damage of the resist pattern can be prevented.

  According to a third aspect of the present invention, there is provided a method for manufacturing a reflective phase shift mask for EUV exposure, wherein the alignment mark is formed in the method for manufacturing a reflective phase shift mask for EUV exposure according to the second aspect. Thereafter, a second resist layer is formed on the hard mask pattern, the second resist layer is formed by electron beam drawing to form the second resist pattern for phase shift means, and the second resist pattern The hard mask pattern is etched using the mask as a mask to form a hard mask pattern for the phase shift means, and the substrate is etched using the hard mask pattern for the phase shift means as a mask to phase shift means to a predetermined position. A stepped region of the concave portion or convex portion of the substrate for use, and then the second resist pattern and the hard mask It is characterized in that the removal of the turn.

  According to the manufacturing method of the reflective phase shift mask for EUV exposure according to the invention described in claim 3, the hard mask layer according to claim 2 is the phase shift means after forming the hard mask pattern for the alignment mark. The present invention can also be applied to the second resist pattern for providing the step region of the concave portion or the convex portion for the purpose, and the generation of the pattern defect due to the damage of the resist pattern can be prevented.

  According to the manufacturing method of a reflective phase shift mask for EUV exposure of the present invention, it is easy to create an alignment mark, and the phase shifter region is drawn at an accurate position by reading the alignment mark dug into the substrate. It is possible to manufacture a Levenson-type reflective phase shift mask that does not damage the multilayer reflective film, does not attenuate EUV reflected light, and reduces manufacturing costs. The contrast is amplified and a high-resolution and high-quality image can be transferred onto the wafer.

It is process sectional drawing which shows one Embodiment of the manufacturing method of the Levenson type reflection type phase shift mask for EUV exposure of this invention. It is process sectional drawing which shows one Embodiment of the manufacturing method of the Levenson type reflection type phase shift mask for EUV exposure of this invention following FIG. FIG. 3 is a partial cross-sectional schematic view showing an embodiment of a Levenson-type reflective phase shift mask according to the manufacturing method of a reflective phase shift mask for EUV exposure according to the present invention. It is a partial cross-sectional schematic diagram which shows other embodiment of the Levenson type reflection type phase shift mask by the manufacturing method of the reflection type phase shift mask for EUV exposure of this invention. In the Example of this invention, it is the figure which calculated | required the relationship between the height of a bump pattern, and the contrast of an optical image by simulation. It is a cross-sectional schematic diagram which shows the conventional Levenson-type reflective phase shift mask for EUV exposure. It is a cross-sectional schematic diagram which shows the other example of the conventional Levenson type reflection type phase shift mask for EUV exposure.

The manufacturing method of a reflective phase shift mask for EUV exposure according to the present invention absorbs EUV light formed on a substrate, a multilayer reflective film reflecting the EUV light formed on the substrate, and the multilayer reflective film. A reflective phase shift mask having an absorber layer, and a region in which the absorber layer is partially removed to form an absorber pattern serving as a transfer pattern for a transfer target, comprising: Forming a first resist pattern on the substrate by electron beam drawing before forming a multilayer reflective film thereon, and etching the substrate to provide an alignment mark made of a concave or convex portion of the substrate at a predetermined position; Then, using the alignment mark as a reference, a second resist pattern is formed by electron beam drawing, and a step region of a concave portion or a convex portion for the phase shift means is provided at a predetermined position of the substrate. The reflected light reflected from the multilayer reflective film surface of the step region has a recess or a phase difference of 180 degrees with the reflected light reflected from the multilayer reflective film surface not provided with the step region. It is the manufacturing method which set the level | step difference of the convex part.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Manufacturing method of reflection type phase shift mask)
FIG. 1 is a process cross-sectional schematic diagram showing an embodiment of a method for producing a Levenson-type reflective phase shift mask for EUV exposure according to the present invention.
First, as shown in FIG. 1A, a hard mask layer 12 is formed on one main surface (front surface) of the substrate 11 as a mask material when the substrate 11 is dry-etched, and then the hard mask layer 12 is formed. A first electron beam resist layer 13 is applied and formed to a predetermined film thickness.

The substrate 11 has a low thermal expansion coefficient to maintain high pattern position accuracy, and has high smoothness and flatness to obtain high reflectivity and transfer accuracy, and is used for cleaning in the mask manufacturing process. A glass substrate such as synthetic quartz glass, SiO ₂ —TiO ₂ type low thermal expansion glass, crystallized glass on which β quartz solid solution is deposited, and the like can be used.

  In the manufacturing method of the present invention, it is possible to form the resist layer 13 directly on the substrate 11 without providing the hard mask layer 12, but the etching depth of the substrate 11 in the region to be the alignment mark is considerably deep. Therefore, the hard mask layer 12 is preferably provided because the resist layer is easily damaged during etching. In addition, the resist layer on the insulating substrate 11 is charged up at the time of electron beam drawing to reduce the resolution and position accuracy of the fine pattern. Therefore, it is more preferable to use a conductive material such as Cr as the hard mask layer 12. preferable.

  As the hard mask layer 12, it is necessary that the hard mask layer 12 has an etching resistance that allows a sufficient selection ratio between the substrate 11 and the etching and can be easily removed after the etching is completed. Examples of the material of the hard mask layer 12 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 of about 10 nm. The chromium-based material has a strong resistance to the fluorine-based gas plasma used for dry etching of the substrate 11 such as a quartz substrate, and can be easily removed by wet etching, and is used by sputtering to a thickness of several tens of nm. It is done.

  Next, as shown in FIG. 1B, a first resist pattern in which an electron beam is drawn by an electron beam drawing apparatus and an opening 14 for an alignment mark is provided at a predetermined position of the first electron beam resist layer 13. 13a is formed.

  Next, the hard mask layer 12 is dry-etched using the first resist pattern 13a as a mask to form a hard mask pattern 12a as shown in FIG. 1C, exposing the substrate surface 15, and 1 resist pattern 13a is peeled and removed. When Cr is used for the hard mask layer 12, a mixed gas of chlorine and oxygen is used as the etching gas.

  Next, using the hard mask pattern 12a as a mask, the exposed substrate 11 is dry-etched to a predetermined depth to form an alignment mark 16 as shown in FIG. When synthetic quartz glass is used for the substrate 11, a fluorine-based gas is used for the etching.

  In the present invention, the alignment mark 16 means an alignment mark for electron beam drawing. When the alignment mark 16 for drawing is formed, an alignment mark for exposure (not shown) used for transferring a mask pattern onto the wafer is also used on the substrate. 11 is preferably formed by etching.

  The alignment mark 16 is a concave or convex portion whose depth or height from the surface of the substrate 11 is in the range of about 50 nm to 500 nm. For example, alignment marks can be formed at the four corners of the substrate 11. FIG. 1 shows a case where the alignment mark 16 is formed as a recess on the surface of the substrate 11. The shape of the alignment mark 16 may be one or more linear recesses arranged in at least one direction, or a recess intersecting with a cross shape.

  Since the alignment mark 16 according to the manufacturing method of the present invention is formed by deep etching the substrate 11, a secondary electron image with high contrast can be detected in mark position detection using an electron beam. Accurate and high-speed alignment is possible.

  Next, a second resist layer is applied and formed on the substrate on which the alignment mark 16 is formed, and an electron beam is drawn using the alignment mark 16 as a reference. As shown in FIG. The second resist pattern 17a is formed. FIG. 1E shows an example in which a resist pattern opening 18 serving as a phase shift region is provided at the center of the second resist pattern 17a.

  Next, using the second resist pattern 17a as a mask, the exposed hard mask pattern 12a is dry-etched, and then the exposed substrate 11 is etched by changing the gas, as shown in FIG. Then, a hard mask pattern 12b having a step region opened by patterning is formed, and a step region 19 of a recess for phase shift means is provided at a predetermined position of the substrate 11. As described above, when Cr is used for the hard mask layer 12, a mixed gas of chlorine and oxygen is used as an etching gas. When synthetic quartz glass is used for the substrate 11, a fluorine-based gas is used for etching. Used. In the above example, the step region 19 for the phase shift means is a concave portion provided on the substrate, but it may be a convex portion provided on the substrate.

The step region 19 is formed by etching the substrate 11 by a depth h, and is formed on the step region when the wavelength of the EUV light is λ and the incident angle of the EUV light to the substrate 11 is θ. The depth h of the recess in the step region such that the EUV reflected light reflected from the surface of the multilayer reflective film causes a phase difference of 180 degrees between the EUV reflected light reflected from the multilayer reflective film surface not provided with the step region. Is represented by the following formula (1) described in Japanese Patent No. 3153230, for example.
h = (2n−1) λ / 4 cos θ (1)
(However, n = 1, 2, 3, ...)

  Here, for example, as a condition for EUV exposure, the wavelength λ of EUV light is 13.5 nm, the incident angle θ of EUV light is 6 °, and from the equation (1), the depth h of the recess in the stepped region is 3.4 nm. Is obtained. Therefore, in the case of the above example, the target depth of the digging of the substrate that generates the phase difference of 180 degrees may be 3 nm to 4 nm.

  Next, the second resist pattern 17 is peeled and removed, and the hard mask pattern 12b is removed by etching to provide an alignment mark 16 and a step region 19 for phase shift means on the substrate 11, as shown in FIG. A processed substrate 10 is obtained.

  In the above process, since the depth of the step region 19 for the phase shift means is relatively shallow, the hard mask pattern 12a is removed by etching after forming the alignment mark 16 in FIG. The second resist layer may be applied and formed directly on the substrate 11. In this case, the second resist pattern can sufficiently withstand the dry etching of the substrate 11. However, as described above, it is more preferable to leave the conductive hard mask pattern 12a in order to prevent charge-up of the substrate during electron beam drawing and to obtain fine pattern accuracy.

FIG. 2 is a process cross-sectional view illustrating an embodiment of a method for producing a Levenson-type reflective phase shift mask for EUV exposure according to the present invention following FIG.
FIG. 2A is the same view as FIG. 1G, and a processed substrate 10 is prepared in which an alignment mark 16 and a step region 19 for phase shift means are provided on a substrate 11.

  Next, as shown in FIG. 2B, a multilayer reflective film 22 that reflects EUV light and an absorber layer 23 that absorbs EUV light are sequentially formed on the processed substrate 10 by a conventionally known method. A film is formed, and a reflective mask blank 20 provided with alignment marks 16 and a step region 19 for phase shift means is formed on the substrate 11.

The multilayer reflective film 22 and the absorber layer 23 are the basic structure of the thin film layer constituting the reflective mask blank to which the manufacturing method of the reflective phase shift mask for EUV exposure of the present invention is applied. FIG. Although not shown, the reflective mask blank to which the present invention can be applied may have other thin film layers. For example, a capping layer that protects the reflective film 22 may be provided on the multilayer reflective film 22, and then a buffer layer may be provided to prevent etching damage to the multilayer reflective film 22 and the capping layer during mask pattern formation. . Further, a low reflection layer having a low reflectance with respect to the inspection light may be formed on the absorber layer 23 in order to increase detection sensitivity when optically inspecting the mask. Further, a conductive layer may be formed on the other main surface (back surface) of the substrate 11 for an electrostatic chuck when the mask is installed in the exposure apparatus.
Hereinafter, each thin film layer constituting the reflective mask blank 20 will be described.

(Multilayer reflective film)
The multilayer reflective film 22 shown in FIG. 2 (b) is made of a material that reflects EUV light (usually having a wavelength of about 13.5 nm) used for EUV exposure with high reflectivity, and molybdenum (Mo) and silicon ( A multilayer film made of Si) is widely used. For example, a reflective film made of a multilayer film in which Mo layers of 2.74 nm thickness and Si layers of 4.11 nm thickness are stacked in 40 layers is mentioned. In the case of a multilayer film composed of Mo and Si, a Si film is first formed in an Ar gas atmosphere using a Si target by a DC magnetron sputtering method, and then a Mo film is used in an Ar gas atmosphere using a Mo target. A multi-layer reflective film can be obtained by stacking 30 to 60 periods, preferably 40 periods.

  In the present invention, in order to give a phase shift effect to all reflected light generated by the multilayer reflective film on the concave portion or convex portion that becomes the step region for the phase shift means and perform high-accuracy transfer, the outermost surface of the multilayer reflective film It is preferable to form the film so that the shape of the step region for the phase shift means is substantially maintained throughout the entire layer. For example, when the film is formed by ion beam sputtering, a desirable multilayer reflective film can be obtained by setting the incident angle of the ion source to about 135 degrees. Of course, the present invention is not limited to this film forming condition, and any other method may be sufficient as long as the concave or convex multilayer reflective film structure serving as the step region for the phase shift means can be obtained up to the outermost surface layer. Effects can be obtained.

(Capping layer)
Although not shown in FIG. 2B, a capping layer for protecting the reflective film may be provided on the multilayer reflective film 22. In order to increase the reflectivity of the multilayer reflective film 22, it is preferable to use Mo having a large refractive index as the uppermost layer. However, Mo is easily oxidized in the atmosphere and the reflectivity is lowered. 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 multilayer reflective film. 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)
Although not shown in FIG. 2B, when the absorber layer 23 that absorbs EUV light is subjected to dry etching to form a pattern, the lower multilayer reflective film 22 and the capping layer are damaged by dry etching. In order to prevent this, a buffer layer may be provided between the multilayer reflective film 22 and the absorber layer 23. As the material of the buffer layer, SiO ₂ , Al ₂ O ₃ , or a chromium-based thin film such as Cr or CrN is used. For example, when forming a chromium-type thin film, it is preferable to form a film with a film thickness in the range of about 5 nm to 20 nm by a DC magnetron sputtering method.

(Absorber layer)
As shown in FIG. 2B, the material of the absorber layer 23 that forms a mask pattern and absorbs EUV light includes tantalum (Ta), tantalum nitride (TaN), tantalum boride (TaB), and boron nitride. A material containing Ta as a main component, such as tantalum (TaBN) or a tantalum / hafnium compound (TaHf), is used in a thickness range of about 35 nm to 60 nm, more preferably in a range of 40 nm to 55 nm. However, the above-mentioned thickness is an example when CrN is used in the buffer layer with a thickness of 10 nm. When the material and thickness of the buffer layer are changed, the thickness of the absorber layer 23 is adjusted according to the buffer layer. There is a need. For example, when the buffer layer has a CrN thickness of 20 nm, it is necessary to reduce the thickness of the absorber layer 23 by about 10 nm.

(Low reflective layer)
Although not shown in FIG. 2B, on the absorber layer 23, when the mask pattern is optically inspected, a low reflection layer that has low reflection with respect to inspection light (for example, wavelength 199 nm or 257 nm). May be 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 ), silicon oxynitride (SiON), chromium nitride (CrN), and the like can be given. 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.

(Conductive layer)
Although not shown in FIG. 2B, a conductive layer is provided on the surface (back surface) opposite to the pattern side of the reflective mask blank 20 for an electrostatic chuck when the mask is installed in the exposure apparatus. There are many things. As a material of the conductive layer, a thin film such as a metal or metal nitride exhibiting conductivity is provided. For example, chromium (Cr), chromium nitride (CrN), tantalum nitride (TaN), or the like has a thickness of 20 nm to A film is formed to a thickness of about 150 nm.

  Here, it returns to description of the manufacturing process of the reflection type phase shift mask of this invention again. As shown in FIG. 2C, a third electron beam resist layer 24 is applied and formed on the absorber layer 23 of the reflective mask blank 20 to a predetermined thickness.

  Next, as shown in FIG. 2D, a predetermined position of the third resist layer 24 is drawn with an electron beam drawing apparatus to form a resist pattern 24a for the absorber pattern.

  Next, the absorber layer 23 is dry-etched using the absorber pattern resist pattern 24a as a mask to form the absorber pattern 23 as shown in FIG. 2E, and the absorber pattern resist pattern 24a is formed. The reflective phase shift mask 27 for EUV exposure is obtained by peeling and removing. Chlorine gas is used for dry etching of the absorber layer 23 when the absorber layer is made of tantalum nitride (TaN), tantalum boride (TaBN), or the like.

  The reflective phase shift mask 27 for EUV exposure shown in FIG. 2E is provided with an alignment mark 26 formed of a recess on the substrate 11 and a step region 25 of a recess for phase shift means at a predetermined position on the substrate. The step of the concave portion is set so that the reflected light reflected from the multilayer reflective film surface in the step region has a phase difference of 180 degrees with the reflected light reflected from the multilayer reflective film surface not provided with the step region. This is a Levenson-type reflective phase shift mask.

  FIG. 3 is a partial cross-sectional schematic view showing an embodiment of a Levenson-type reflective phase shift mask according to the method of manufacturing a reflective phase-shift mask for EUV exposure according to the present invention. As in FIG. 2E, the reflective phase shift mask 30 shown in FIG. 3 includes an alignment mark 36 formed of a recess on the substrate 31 and a step region 35 of the recess for the phase shift means at a predetermined position on the substrate. The step of the recess is so formed that the reflected light reflected from the multilayer reflective film surface of the step region has a phase difference of 180 degrees with the reflected light reflected from the multilayer reflective film surface not provided with the step region. Is a Levenson-type reflection type phase shift mask.

FIG. 4 is a partial cross-sectional schematic view showing another embodiment of the Levenson-type reflection-type phase shift mask according to the manufacturing method of the reflection-type phase shift mask for EUV exposure of the present invention. The reflective phase shift mask 40 shown in FIG. 4 is provided with an alignment mark 46 formed of a convex portion on a substrate 41 and a convex step region 45 for phase shift means at a predetermined position of the substrate. A Levenson-type step where the step of the convex portion is set so that the reflected light reflected from the multilayer reflective film surface has a phase difference of 180 degrees between the reflected light reflected from the multilayer reflective film surface not provided with the step region. It is a reflective mask.
Hereinafter, the present invention will be described in more detail with reference to examples.

In this example, a Levenson-type reflective phase shift mask for EUV exposure was prepared in which a step region of convex portions (hereinafter referred to as bumps) was provided on a mask substrate for phase shift means.
As the mask substrate, a SiO ₂ —TiO ₂ -based LTEM (Low Thermal Expansion Material) substrate was used, and the relationship between the height of the bump pattern and the contrast of the optical image in EUV exposure was first determined by simulation.

(Evaluation tool)
In order to estimate the transfer characteristics of the mask pattern, EM-Suite (trade name: manufactured by Panoramic Technology) was used as simulation software. In addition, a three-dimensional electromagnetic field simulation of a Levenson-type EUV exposure phase shift mask is performed by the FDTD method (also referred to as a time-domain difference method or a finite-difference time-domain method) using TEMPESTpr2 (EM-Suite option). A model was used. The simulation grid for analyzing the electromagnetic field in the mask was 1 nm on the mask dimension. In the FDTD method, the Maxwell equation is differentiated with respect to time and space, and the difference equation is calculated alternately for the magnetic field and the electric field until the electromagnetic field in the region stabilizes. Various phenomena such as the effects of the Levenson structure are highly accurate. It is a method that can be reproduced.

  The absorber layer of the EUV exposure mask was tantalum nitride (TaN), and its thickness was 70 nm. The capping layer was ruthenium (Ru), and its thickness was 2.5 nm. The multilayer reflective film is a multilayer film made of silicon (Si) and molybdenum (Mo), and has 40 layers with a period of 7 nm (Si 4.2 nm, Mo 2.8 nm). The values in Table 1 below were used for the refractive index n and extinction coefficient k of the elements and compounds constituting each layer.

(Exposure conditions)
As an illumination condition of the Levenson type EUV exposure phase shift mask, in this embodiment, EUV light with an exposure wavelength of 13.5 nm is used in EUV exposure with a half pitch of 22 nm, and the numerical aperture (NA) of the projection lens is 0.25. did. The half pitch of the bump pattern to be a convex portion was also 22 nm. Half pitch 22 nm is a region where sufficient contrast cannot be obtained under the conditions of NA of 0.25 and exposure wavelength of 13.5 nm, and the performance of the Levenson type EUV exposure phase shift mask according to the manufacturing method of the present invention is evaluated. It is a suitable pattern to do. As illumination conditions, normal illumination with a coherent factor (σ) of 0.5 in the illumination system was used. The incident angle of EUV light to the mask substrate was 6 degrees.

  A simulation is performed under the above exposure conditions, and the relationship between the height (Height; nm) of the bump (convex part) pattern made to cause a phase change on the LTEM substrate and the contrast (Contrast) of the optical image in EUV lithography is shown. As shown in FIG. As shown in FIG. 5, it can be seen that no contrast is obtained when the bump height is 0 nm, but a contrast of 0.6 is obtained when the bump height is around 3 nm. Furthermore, the tolerance of the bump height at which a contrast of about 0.5 to 0.6 can be obtained also has a margin of 1 nm to 4 nm and 3 nm, and it is considered that there is sufficient manufacturing tolerance.

(Manufacture of Levenson-type reflective phase shift mask for EUV exposure)
Based on the simulation results, a Levenson-type reflective phase shift mask for EUV exposure was manufactured by the following procedure.

(Production of processed substrate)
On one main surface of a 6 inch square and 0.25 inch thick LTEM substrate, a Cr film was sputtered as a mask material for dry etching the substrate, and a hard mask layer having a thickness of 60 nm was formed. Then, a first electron beam resist layer was applied and formed to a thickness of 300 nm on the hard mask layer.

  Next, electron beam drawing was performed by an electron beam drawing apparatus, and a first resist pattern for alignment marks was formed at four locations around the substrate of the first electron beam resist layer.

  Next, using the first resist pattern as a mask, the hard mask layer Cr is dry-etched with a mixed gas of chlorine and oxygen to form a Cr hard mask pattern, exposing the substrate surface, and then the first resist pattern Was removed.

  Next, using the hard mask pattern as a mask, the exposed substrate is dry-etched to a depth of 50 nm using a fluorine-based gas to form a protrusion (bump) -shaped alignment mark having a height of 50 nm on the substrate. The Cr hard mask pattern was removed by etching.

  Next, a second electron beam resist layer is applied and formed to a thickness of 300 nm on the substrate on which the alignment mark is formed, an electron beam is drawn on the basis of the alignment mark, and a second resist pattern for the phase shift means is formed. Formed.

  Next, using the second resist pattern as a mask, the exposed substrate is dry-etched using a fluorine-based gas, patterned, and a step of a bump (bump) for phase shift means is formed at a predetermined position on the substrate. A bump pattern having regions was formed. Based on the simulation results, the bump height of the bump pattern by etching was set to 3 nm.

  Next, the second resist pattern was peeled and removed to obtain a processed substrate provided with an alignment mark and a bump pattern with a half pitch of 22 nm serving as a convex stepped region for the phase shift means.

(Manufacture of mask blank)
Next, on the above processed substrate, a multilayer film composed of Si and Mo that reflects EUV light, a multilayer reflective film composed of 40 layers with a period of 7 nm (thickness: Si 4.2 nm, Mo 2.8 nm), and multilayer reflection A capping layer having a thickness of 2.5 nm made of Ru that protects the film and an absorber layer having a thickness of 70 nm made of TaNO that absorbs EUV light are sequentially formed by a conventionally known method, and an alignment mark and a phase are formed on the substrate. A reflective mask blank provided with a step region for the shift means was formed.

(Manufacture of mask)
Next, a third electron beam resist layer was formed to a thickness of 180 nm on the absorber layer TaNO of the reflective mask blank.

  Next, a predetermined position of the third resist layer was drawn with an electron beam drawing apparatus based on the alignment mark, thereby forming a resist pattern for an absorber pattern with a half pitch of 22 nm.

  Next, using the resist pattern for absorber pattern as a mask, the absorber layer is dry-etched using fluorine-based gas and chlorine-based gas to form an absorber pattern, and the resist pattern for absorber pattern is peeled and removed. Thus, a Levenson type reflective phase shift mask for EUV exposure was obtained.

  FIG. 4 is a partial cross-sectional schematic diagram showing a Levenson-type reflective phase shift mask obtained by the manufacturing method of a reflective phase shift mask for EUV exposure according to the present embodiment. The reflective phase shift mask 40 shown in FIG. 4 is provided with an alignment mark 46 formed of a convex portion on a substrate 41 and a convex step region 45 for phase shift means at a predetermined position of the substrate. A Levenson-type step where the step of the convex portion is set so that the reflected light reflected from the multilayer reflective film surface has a phase difference of 180 degrees between the reflected light reflected from the multilayer reflective film surface not provided with the step region. It is a reflective mask. However, FIG. 4 shows only one alignment mark 46 made of a convex portion and one step region 45 of the convex portion (bump).

  When the EUV exposure is performed using the reflective phase shift mask according to the present embodiment, the contrast of light at the time of pattern transfer is amplified by the phase shift effect, and a high-resolution, high-quality image can be transferred onto the wafer. did it.

DESCRIPTION OF SYMBOLS 10 Processed substrate 11 Substrate 12 Hard mask layer 12a Hard mask pattern 12b Hard mask pattern 13 which opened the level | step difference area | region 1st electron beam resist layer 13a 1st resist pattern 14 Alignment mark opening part 15 Substrate surface 16 Alignment mark 17a First 2 resist pattern 18 resist pattern opening 19 step region 20 reflective mask blank 22 multilayer reflective film 23 absorber layer 24 third electron beam resist layer 24a third resist pattern 25 step region 26 alignment mark 27 reflective mask 30 , 40 Reflective mask 31, 41 Substrate 32, 42 Multilayer reflective film 33, 43 Absorber layer 35, 45 Step region 36, 46 Alignment mark 1- (1) First multilayer film 1- (2) Second multilayer Film 2- (1) First protective film 2- (2) Second Protective film 3 Intermediate film 4 Absorbing film 5 Substrate

Claims (3)

A substrate, a multilayer reflective film that reflects the EUV light formed on the substrate, and an absorber layer that absorbs the EUV light formed on the multilayer reflective film, the absorber layer being the absorber A method of manufacturing a reflective phase shift mask for EUV exposure having a region in which an absorber pattern serving as a transfer pattern for a transfer target is formed by partially removing a layer,
Before forming the multilayer reflective film on the substrate, a first resist pattern is formed on the substrate by electron beam drawing, and the substrate is etched to align the concave portion or the convex portion of the substrate at a predetermined position. Providing a mark;
Forming a second resist pattern by electron beam drawing on the basis of the alignment mark, and providing a step region of a concave portion or a convex portion for phase shift means at a predetermined position of the substrate;
The reflected light of the EUV light reflected from the multilayer reflective film surface of the step region has a phase difference of 180 degrees between the reflected light reflected from the multilayer reflective film surface not provided with the step region. A method of manufacturing a reflective phase shift mask for EUV exposure, wherein a step of a concave portion or a convex portion is set. In the step of forming the first resist pattern on the substrate by electron beam drawing,
After forming a hard mask layer on the substrate, a first resist layer is formed, and the first resist layer is drawn with an electron beam to form the first resist pattern for alignment marks, After forming the hard mask pattern for the alignment mark by etching the hard mask layer using the resist pattern of 1 as a mask, the first resist pattern is peeled off and using the hard mask pattern for the alignment mark as a mask The method of manufacturing a reflective phase shift mask for EUV exposure according to claim 1, wherein the substrate is etched to provide an alignment mark made of a concave or convex portion of the substrate at a predetermined position.   3. The method of manufacturing a reflective phase shift mask for EUV exposure according to claim 2, wherein after forming the alignment mark, a second resist layer is formed on the hard mask pattern, and the second resist layer is formed as an electron. Drawing the line to form the second resist pattern for the phase shift means, etching the hard mask pattern using the second resist pattern as a mask to form a hard mask pattern for the phase shift means, The substrate is etched using the hard mask pattern for the phase shift means as a mask to provide a stepped region of the concave portion or the convex portion of the substrate for the phase shift means at a predetermined position, and then the second resist pattern and the hard A method of manufacturing a reflective phase shift mask for EUV exposure, wherein the mask pattern is removed.

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