JP2004273689A - Exposure mask, method for manufacturing the same and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure mask in which a pattern form is correctly retained to effect high precision pattern transfer, to provide a method for manufacturing the exposure mask, and to provide a method for manufacturing a semiconductor. <P>SOLUTION: A silicon nitride film 7 is laminated on a membrane consisting of a silicon layer 4 having the (100) plane parallel to the surface, and an opening width W<SB>1</SB>of a large diameter part 6a is formed in the silicon nitride film 7 as a passing hole 6, followed by a wet etching with KOH solution using the part 6a as a mask. Difference in etching rate allows the wall surface of the passing hole 6 in the silicon layer 4 is formed on the (111) plane with an inclination at a certain angle, resulting in reducing the passing hole 6 to have a considerably precise opening width W<SB>2</SB>at an aperture part 6b, followed by coating the surface of the silicon nitride film 7, the inner wall surface of the passing hole 6 and the lower surface of the silicon layer 4 with a metal film 10. Thus, in carrying out EPL, since foreign substances 21 in the air attach to the metal film 10, the form of the aperture part 6b is retained, pattern transfer with high precision becomes possible. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure mask, a method for manufacturing the same, and a method for manufacturing a semiconductor device, and more particularly, to a stencil mask for electron beam transfer lithography, a method for manufacturing the same, and a semiconductor device using a mask for electron beam transfer lithography. It relates to a manufacturing method.
[0002]
[Prior art]
2. Description of the Related Art With the miniaturization and high integration of LSIs, the practical application of electron beam projection lithography (EPL) is expected. Examples of EPLs that are being put into practical use include PREVAIL (projection exposure with variable axes immersion lenses) and LEEPL (low energy electron beam projection profiling scheme).
[0003]
As a mask used for the EPL, a stencil mask having a hole (aperture) in a part of a thin film (membrane) and a membrane mask having a heavy metal layer in a part of the membrane have been proposed. In the case of a stencil mask, an electron beam passes through the aperture. In the case of a membrane mask, an electron beam is scattered by the heavy metal layer, and the electron beam passes through a portion where the heavy metal layer is not formed.
[0004]
Since PREVAIL uses an electron beam of about 100 keV, both a stencil mask and a membrane mask can be used. On the other hand, an electron beam of about 2 keV is used for LEEPL. Since the energy of the electron beam is low, the electron beam does not pass through the membrane mask. Therefore, in the case of LEEPL, a stencil mask is used.
[0005]
The stencil mask for PREVAIL has an aperture corresponding to the pattern on a 2 μm thick silicon membrane. PREVAIL is typically a 4 × reduction projection system. The electron beam passes through only the aperture portion without scattering, and forms an image on the resist. Thus, the resist is exposed in a predetermined pattern.
[0006]
The stencil mask for LEEPL has an aperture corresponding to a pattern on a silicon or diamond membrane having a thickness of 500 nm. LEEPL is a unit magnification projection system. The electron beam transmits only through the aperture, and the pattern is transferred to the resist.
[0007]
FIG. 7 is a sectional view of a conventional stencil mask. This stencil mask 1B has, for example, a mask portion 4a of a predetermined size on a silicon wafer 2, a beam called a strut 12 is formed around the mask portion 4a, and the mask portion 4a has a mask. An aperture 6 corresponding to the pattern is formed. By forming the aperture 6 in the mask portion 4a, the mechanical strength of the mask portion 4a is significantly reduced, so that the strut 12 acts as a support for reinforcing the mechanical strength of the stencil mask 1B.
[0008]
When the stencil mask 1B is formed using a silicon wafer, an SOI wafer 5 on which a silicon wafer 2, a silicon oxide film 3 and a silicon layer 4 are stacked is used, and the height of the strut 12 is, for example, 725 μm. The mask portion 4a is a part of the silicon layer 4, and the surface of the silicon layer 4 is usually a (100) plane. The silicon oxide film 3 functions as an etching stopper when the back surface of the silicon wafer 2 is etched to form the strut 12.
[0009]
In such a conventional method of manufacturing a stencil mask, an aperture is formed by dry etching using a resist as a mask, and the dry etching is performed without considering the crystal plane of the membrane material. Further, the cross-sectional shape of the aperture has been controlled by adjusting etching conditions such as the composition of an etching gas.
[0010]
As a result, when the pattern is transferred using the stencil mask 1B, the edge roughness of the resist pattern is transferred to the mask as it is, causing a pattern defect. Further, since the cross-sectional shape of the aperture changes according to the etching conditions, the cross-sectional shape does not always have a vertical cross-sectional shape as shown in FIG. 7 and the cross-section is tapered or the diameter of the aperture is large near the center in the height direction. Sometimes it was.
[0011]
Therefore, as a technique for manufacturing such a fine pattern with high precision, a large-width opening is formed in the silicon nitride film provided on the silicon layer 4 by dry etching, and the silicon layer 4 forming the mask portion 4a is formed by wet etching. It is disclosed that the aperture 6 is formed to form the aperture 6 reduced at a certain angle (see Patent Document 1 described later).
[0012]
In Patent Document 1 (hereinafter, referred to as a prior application invention) proposed by the present applicant, the surface of a silicon layer of an SOI wafer is a (100) plane, and a plane crossing the silicon layer is a (111) plane. When a transmission hole for an electron beam is formed in this silicon layer because of a crystal film, the etching rate is lower on the (111) plane than on the (100) plane, and the transmission hole reduced at a certain angle is formed. The configuration is shown in FIG.
[0013]
6A and 6B show a stencil mask according to the prior application, wherein FIG. 6A is a partial cross-sectional view, FIG. 6B is an enlarged view of a portion A in FIG. 6A, and FIG. 6C is a schematic cross-sectional view showing a use state. .
[0014]
That is, as shown in FIG. 6A, this stencil mask 1A has a mask portion 4a having a size of 25 mm square on a strut 12 formed of a silicon wafer 2. An aperture 6 corresponding to the mask pattern is formed in the mask section 4a. By forming the aperture 6 in the mask portion 4a, the mechanical strength of the mask portion 4a is reduced, so that the strut 12 functions as a support for reinforcing the mechanical strength of the stencil mask 1A.
[0015]
The mask portion 4a of the stencil mask 1A includes a silicon layer 4, a silicon nitride film 7, a first metal layer 16, a second metal layer 17, and a third metal layer 18. As shown, the first metal layer 16 is also formed on the lower surface of the silicon layer 4 and the lower surface of the strut 12, the second metal layer 17 is formed on the silicon nitride film 7, and the third metal layer 18 Is formed at least on the wall surface of the aperture 6 in the silicon layer 4 portion.
[0016]
The silicon nitride film 7 and the first to third metal layers 16, 17, 18 are provided as membrane support layers for improving the mechanical strength of the mask portion 4a and the like. Further, by forming the first to third metal layers 16, 17, and 18, it is possible to prevent the stencil mask 1A from being charged (charge-up) at the time of performing the EPL, thereby preventing the position of the incident electrons from being shifted. Can be. As long as reinforcement of the membrane and prevention of charge-up can be achieved, a conductive layer made of a material other than metal may be formed.
[0017]
As shown in FIG. 6B, at the interface between the silicon layer 4 and the silicon nitride film 7, the surface of the silicon layer 4 is a (100) plane. The cross section of the silicon layer 4 with respect to the aperture 6 is a (111) plane. That is, the aperture 6 is formed in consideration of the crystal plane orientation of the membrane material. Thus, the angle between the interface between the silicon layer 4 and the first metal layer 16 and the (111) plane, which is a cross section of the silicon layer 4, is 54.7 °.
[0018]
Thus, by controlling the taper angle of the aperture 6 using the crystal plane orientation of the membrane material, the taper angle can be kept constant even when the pattern is further miniaturized. Opening width W of aperture 6 ₂ Is the opening width W in the silicon nitride film 7. ₁ , The thickness d of the silicon layer 4 and the taper angle.
[0019]
Therefore, the opening width W is formed in the silicon nitride film 7. ₂ Even if the resist cannot be formed, the opening width W ₁ Can be formed, the opening width W ₁ Opening width W of aperture 6 smaller than ₂ Can form a mask pattern. Further, since the taper angle of the aperture is constant, the opening width W ₁ Is precisely reduced to the opening width W ₂ Is formed.
[0020]
This makes it possible to flatten the cross section of the hole on the order of the atomic layer. Further, by using the silicon layer 4 of a single crystal film having a (100) plane parallel to the surface, the wall surface of the aperture 6 is formed on the (111) plane, and the taper angle of the hole is set to a predetermined angle (54.7 °). ), The strength of the thin film is reinforced by providing the first to third metal layers 16, 17, 18 on the surface of the thin film, and a mask for performing charged particle beam lithography is provided. Charge up can be prevented.
[0021]
FIG. 6C is a schematic cross-sectional view showing an example of equal-size transfer using the stencil mask 1A. For example, an SOI in which a silicon oxide film 23 and an aluminum film as a wiring layer 24 are sequentially stacked on a silicon substrate 22 is shown. A negative-type electron beam resist layer 25 is disposed on the wafer 20, a stencil mask 1A is disposed thereon at a distance of C (about 50 μm), and the upper surface of the stencil mask 1A is irradiated with, for example, an electron beam 18. . The irradiated electron beam 18 passes through the aperture 6 of the stencil mask 1A and is transferred to the electron beam resist film 25 on the wafer 20.
[0022]
As described above, in the stencil mask of the prior application, the cross-sectional shape of the aperture and the flatness of the cross-section are controlled with high precision, and a fine mask pattern is formed with high precision. The transfer to the semiconductor device makes it possible to reduce the roughness of the LSI circuit pattern and to manufacture a device having few pattern defects, for example. Further, the provision of the membrane support layer has excellent features such as improvement in durability of the thin film against stress and heat.
[0023]
[Patent Document 1]
JP-A-2002-343710 (page 5, right column, page 8, right and left columns, FIGS. 1 and 2)
[0024]
[Problems to be solved by the invention]
However, fine foreign matter floating not only in the indoor air but also in a fine space such as the inside of the pattern transfer mechanism adheres to the pattern opening wall surface of the mask, and the adhered foreign matter peels off to open the opening. Since the pattern shape is deformed by closing or the like, measures to prevent this are an important problem. However, while miniaturization of patterns has progressed, it has become difficult to take measures against dust particles.
[0025]
As one of dust prevention measures, for example, as shown in FIG. 8, a transparent protective film provided at a position of a fixed distance (standoff) D with respect to a pattern surface 28 of a mask (or reticle) 27 arranged on a frame 26. And a pellicle (thin film) configured to prevent foreign matter from adhering to the mask 27.
[0026]
However, the pellicle does not transmit the electron beam, so it cannot be applied to all steppers. For example, as a next-generation electron beam lithography technology, a pellicle cannot be applied to LEEPL (low energy electron beam projection projection lithography) using an electron beam as a light source for exposure. As described above, in reality, there is no method for positively preventing foreign matter adhering to a mask.However, this problem is not an exception in the prior invention having excellent features as described above, but in the prior invention, However, there is no foreign substance removal measure, and the establishment of a solution is urgently demanded.
[0027]
If exposure is performed using a stencil mask with insufficient measures for removing foreign matter, the following problems (1) and (2) may occur.
(1) The shape of the pattern is deformed by a foreign substance attached to the pattern opening.
(2) When exposure is performed with the pattern shape deformed, especially in the case of LEEPL, since the same-size transfer is performed, the shape of the foreign substance itself is transferred to the photosensitive layer, and the shape of the transfer pattern is changed.
The shape will be greatly deformed, and the transfer accuracy will be degraded.
[0028]
The present invention has been made in view of the above circumstances, and while maintaining the excellent features of the prior invention, the pattern shape is more accurately retained, and an exposure mask capable of pattern transfer with high accuracy and It is an object of the present invention to provide a method for manufacturing the same and a method for manufacturing a semiconductor device.
[0029]
[Means for Solving the Problems]
That is, the present invention provides an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern.
A single crystal film having a first lattice plane parallel to the film surface;
At least the single crystal film and a support supporting the single crystal film on the one surface side.
A thin film comprising:
The exposure beam passage hole formed in the thin film,
Forming a wall surface of the exposure beam passage hole of the single crystal film, and reducing the exposure beam passage hole in the single crystal film from the one surface side to the other surface side;
A second lattice plane,
At least substantially the entire inner wall surface of the exposure beam passage hole, and the one surface
A conductive film covering the
The present invention relates to an exposure mask (hereinafter, referred to as an exposure mask of the present invention).
[0030]
According to the exposure mask of the present invention, an exposure beam passage hole formed in a thin film including a single crystal film having a first lattice plane parallel to the film surface and a support layer supporting the single crystal film on one surface side is formed. Since the wall surface is formed in the single crystal film and is formed on the second lattice plane of the single crystal film by being reduced from one surface side to the other surface side, the wall surface is formed flat, Since the pattern opening formed by the wall surface is controlled and reduced to a certain angle formed by the first and second lattice planes, the width of the passage hole in the single crystal film is formed with high precision. In addition, since at least almost the entire inner wall surface of the exposure beam passage hole and the one surface are covered with the conductive film, the conductive film is formed of a material having a high foreign matter adhesion property. The foreign matter easily adheres to the conductive film, and the foreign matter that enters the through hole from the one surface side adheres to the conductive film on one surface and the conductive film on the inner wall surface of the through hole. Since it does not adhere to the pattern opening to be formed, the shape of the pattern opening can be maintained, and the mechanical strength of the exposure mask can be increased by the conductive film.
[0031]
Further, the present invention provides a method of manufacturing an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern.
A support layer for supporting the single crystal film on the one surface side on a single crystal film having a first lattice plane parallel to the film surface and a second lattice plane intersecting the first lattice plane To
Forming,
Forming a first passage hole corresponding to the exposure beam passage hole in the support layer;
When,
The single crystal film is etched through the first passage hole, and the exposure beam passage hole is reduced from the one surface side to the other surface below the first passage hole.
Forming a second passage hole comprising the second lattice plane,
Covering at least substantially the entire inner wall surface of the exposure beam passage hole formed by the first passage hole and the second passage hole, and the one surface with a conductive film.
When
The present invention relates to a method for manufacturing an exposure mask (hereinafter, referred to as a method for manufacturing an exposure mask of the present invention).
[0032]
According to the method of manufacturing an exposure mask of the present invention, a support layer for a single crystal film is formed on a single crystal film having a first lattice plane parallel to the film surface and a second lattice plane intersecting the first lattice plane. Is formed in the support layer, and a first through-hole is formed in the support layer, and the first through-hole is reduced through the first through-hole by etching from the one surface to the other under the first through-hole. Since the second passage hole composed of the second lattice surface is formed, the wall surface of the second passage hole can be formed flat, and the pattern opening formed by the wall surface is formed by the first and second lattice surfaces. Since the size is controlled to be constant and reduced, the width of the passage hole in the single crystal film can be formed with high precision. In addition, since at least almost the entire inner wall surface of the exposure beam passage hole and the one surface are covered with a conductive film, the conductive film is formed of a material having a high adhesion to foreign substances. Foreign matter easily adheres to the membrane, and foreign matter entering the through-hole from the one surface side adheres to the conductive film on one surface and the conductive film on the inner wall surface of the through-hole to form the reduced through-hole. Since it does not adhere to the pattern opening, the shape of the pattern opening can be maintained, and the mechanical strength of the exposure mask can be increased by the conductive film.
[0033]
Further, the present invention provides a method of manufacturing a semiconductor device using an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern.
A single crystal film having a first lattice plane parallel to the film surface;
At least the single crystal film and a support supporting the single crystal film on the one surface side.
A thin film comprising:
The exposure beam passage hole formed in the thin film,
Forming a wall surface of the exposure beam passage hole of the single crystal film, and reducing the exposure beam passage hole in the single crystal film from the one surface side to the other surface side;
A second lattice plane,
At least substantially the entire inner wall surface of the exposure beam passage hole, and the one surface
A conductive film covering the
Using an exposure mask having
The present invention relates to a method of manufacturing a semiconductor device (hereinafter, referred to as a method of manufacturing a semiconductor device of the present invention), which comprises exposing a photosensitive layer on a semiconductor substrate to a predetermined pattern.
[0034]
According to the method of manufacturing a semiconductor device of the present invention, an exposure mask used for exposing a photosensitive layer on a semiconductor substrate is manufactured in the same manner as the above-described method of manufacturing an exposure mask of the present invention. With the same effect as the method, a predetermined pattern can be transferred onto the photosensitive layer on the semiconductor substrate with high precision, and a semiconductor device can be manufactured with high reliability.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
In the above-described exposure mask, the method for manufacturing the exposure mask, and the method for manufacturing the semiconductor device according to the present invention, the mechanical strength of the exposure mask is such that the other surface of the single crystal film is also covered with a conductive film. This is desirable in that dust can be further increased, and foreign matter flying from the surface to be transferred or the like can be attached to improve dustproofing efficiency.
[0036]
Further, the other surface side of the single crystal film is supported by a support portion, and a third passage hole larger than the mask portion including the exposure beam passage hole is formed in the support portion. This is desirable because the conductive film on the side can be easily formed and the mechanical strength of the exposure mask can be easily reinforced.
[0037]
The first lattice plane of the single crystal film may be a (100) plane or a (110) plane, and the second lattice plane may be a (111) plane. The holes are desirably reduced in that the holes are inclined at a certain angle and can be reduced to form a passage hole having a desired width with high precision.
[0038]
In this case, by forming the first through-hole by dry etching and forming the second through-hole by wet etching, the second through-hole can be reduced and formed using a difference in etching rate. Desirable in point.
[0039]
Further, it is preferable that the conductive film is made of at least one of platinum, palladium, and iridium having foreign substance adhesion property, or an alloy containing them, or a laminate of these metals. Is desirable because it is easy to hold
[0040]
In this case, the deposited particles are caused to fly from different directions to the exposure beam passage hole by sputtering or vapor deposition, and the deposited particles are also caused to fly to the other surface side of the single crystal film to adhere the conductive film. Is desirable in that the foreign matter removing effect can be enhanced.
[0041]
Preferably, the exposure beam is a charged particle beam such as an electron beam.
[0042]
Then, an exposure mask is manufactured as described above, pattern transfer by an electron beam is performed using the exposure mask, an etching mask is formed by developing the photosensitive layer exposed to a predetermined pattern, and the semiconductor mask is formed by the etching mask. By etching the layer to be etched on the base, a semiconductor device can be manufactured with high reliability.
[0043]
Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.
[0044]
FIG. 1 is a schematic sectional view showing a part of a stencil mask 1 as an exposure mask according to the present embodiment, and is a view corresponding to FIG. Note that the same reference numerals are used for the same portions as those of the prior application and the like.
[0045]
As shown in FIG. 1, the stencil mask 1 of the present embodiment is different from the prior invention in that the front surface (one surface) 8 of the stencil mask 1, the inner wall surface 6a of the exposure beam passage hole 6, and the back surface (the other surface) are provided. Surface 9) is covered with the metal film 10. Other configurations are almost the same as those of the prior application. That is, the stencil mask 1 of the present embodiment is obtained by adding a desired function to the stencil mask of the prior application by partially forming a new structure.
[0046]
Therefore, the opening width W of the large diameter portion 6a as the first passage hole formed in the silicon nitride film 7 in the passage hole 6 in FIG. ₁ In contrast, the opening width W of the aperture portion 6b as a second passage hole formed in the silicon layer (membrane) 4 ₂ Is formed through a process similar to that of the prior invention, so that it has the same accuracy as that of the prior application, and the metal film 10 is provided on the entire inner wall surface of the passage hole 6 to reduce the surface area. Since foreign matter entering the through hole 6 from the side 8 is attached to the metal film 10, the foreign matter does not adhere to the aperture portion 6b, and the pattern shape can be maintained.
[0047]
Such a configuration is manufactured through the same process as the invention of the prior application except for the formation of the metal film 10. 2 to 4 show this manufacturing process.
[0048]
First, as shown in FIG. 2A, a silicon nitride film 7 is formed on the surface of an SOI wafer 5 having a (100) surface, and a silicon layer 4 as a membrane and a silicon nitride film 7 supporting the silicon layer 4 are formed. Is formed.
[0049]
The SOI wafer 5 has a (100) silicon layer 4 on the silicon wafer 2 with a silicon oxide film 3 interposed therebetween. The thickness of the silicon wafer 2 is, for example, 725 μm, the thickness of the silicon oxide film 3 is, for example, 100 nm, and the thickness of the silicon layer 4 is, for example, 50 nm. The thickness of the silicon layer 4 depends on the energy of the electron beam when performing the EPL using the stencil mask and the opening width conversion amount (W) of the aperture portion 6b in FIG. ₁ -W ₂ ) May be changed as appropriate.
[0050]
The silicon nitride film 7 is formed by, for example, chemical vapor deposition (CVD). The thickness of the silicon nitride film 7 is, for example, 500 nm. The silicon nitride film 7 serving as a membrane support layer is not etched by an etchant when etching the silicon layer 4 and is made of any material that can support a membrane having a size (for example, 25 mm square) corresponding to a chip region. The material and thickness can be changed.
[0051]
The stencil mask 1 according to the present embodiment is intended to prevent the mask pattern from being deformed due to the intrusion of foreign matter, and the effect of removing foreign matter is particularly the inner wall of an exposure beam passage hole (hereinafter sometimes referred to as a passage hole) 6. Depends on the area. Therefore, the thicker the silicon nitride film 7 is, the larger the inner wall area of the through hole 6 can be. However, if the thickness is too large, it becomes difficult to perform the oblique vapor deposition of the metal film described later satisfactorily. To decide. Further, by forming the stencil mask 1 thick, the strength of the stencil mask 1 can be maintained even when the silicon layer 4 as the membrane is thin.
[0052]
When potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) is used as an etchant for the silicon layer 4, for example, silicon carbide, silicon oxide, silicon oxynitride may be used instead of the silicon nitride. A layer of a film, diamond, DLC (diamond like carbon), metal, or the like may be formed with a thickness of about 100 to 3000 nm. In this case, the thicker the layer, the greater the dustproof effect.
[0053]
Next, as shown in FIG. 2B, a resist film 14 is formed on the silicon nitride film 7. The opening width W of the large diameter portion 6a of the exposure beam passage hole 6 formed by the interval between the resist films 14. ₁ Is the opening width W of the aperture portion 6b formed in the silicon layer 4 shown in FIG. ₂ Wider than Subsequently, the pattern of the resist film 14 is transferred to the silicon nitride film 7 by etching the silicon nitride film 7 using the resist film 14 as a mask. This etching is dry etching using, for example, CF4. After that, the resist film 14 is removed.
[0054]
Next, as shown in FIG. 2C, wet etching is performed on the silicon layer 4 using the silicon nitride film 7 as a mask. For example, when the wafer is immersed in a KOH solution having a concentration of 30 wt% and a temperature of 70 ° C., the etching rate of the (100) plane silicon is 797 nm / min, whereas the etching rate of the (111) plane silicon is 5 nm / min. Extremely slow.
[0055]
That is, while the etching proceeds quickly in the vertical direction of the silicon layer 4, the etching hardly proceeds near the silicon nitride film 7. Therefore, the etched section of the silicon layer 4 has a tapered shape corresponding to the (111) plane, and the (111) plane has an angle of 54.7 ° with respect to the (100) plane of the silicon layer 4.
[0056]
As a result, the opening width W of the aperture portion 6b at the lower end of the silicon layer 4 ₂ Is the opening width W of the large diameter portion 6a of the resist film 14 or the silicon nitride film 7. ₁ Narrower than. When the thickness of the silicon layer 4 is d,
W ₂ = W ₁ -2d / tan 54.7 °
And the opening width W ₁ Is the opening width W according to the thickness d of the silicon layer 4. ₂ Is reduced to
[0057]
In the present embodiment, since the thickness d of the silicon layer 4 is 50 nm, for example, the opening width W in the resist film 14 or the silicon nitride film 7 is set. ₁ To 105.8 nm, W ₂ = 35 nm fine pattern is formed with high precision.
[0058]
When the aperture is formed by utilizing the difference in the etching rate depending on the crystal plane as described above, the cross-sectional shape of the aperture is flattened in the order of an atomic layer, or the aperture is processed with a cross-sectional shape having a predetermined taper angle. Can be. Further, in the present embodiment, the difference in the etching rate with respect to the (111) plane of the silicon layer 4 having the (100) plane is used. However, if there is a difference in the etching rate, any combination of crystal planes can be used.
[0059]
Even if a TMAH solution is used as an etchant when performing wet etching on the silicon layer 4, the etching rate changes according to the crystal plane. For example, when the wafer is immersed in a TMAH solution having a concentration of 20 wt% and a temperature of 80 ° C., the etching rate of silicon is 603 nm / min on the (100) plane, 1114 nm / min on the (110) plane, and 17 nm / min on the (111) plane. Become. Therefore, similarly to the case where a KOH solution is used, a specific crystal plane can be selectively etched, and the flatness and shape of the aperture cross section can be controlled with high precision.
[0060]
Next, as shown in FIG. 3D, a silicon oxide film 13 is laminated on the back surface of the silicon wafer 2, and a resist is further applied and exposed to form a resist film 15 for forming struts.
[0061]
Next, as shown in FIG. 3E, the silicon wafer 2 is etched from the back side with BHF (buffered hydrofluoric acid) or the like using the resist 15 as a mask, so that the silicon oxide film 13 other than under the resist film 15 becomes resist. Since the silicon wafer 2 is etched using the remaining silicon oxide film 13 as a mask, the strut 12 is formed so as to surround the pattern transfer region, and the silicon layer 4 in the mask portion 4a is removed. Exposed. The silicon oxide film 13 on the back side is not necessarily provided, but if dry etching is performed without the silicon oxide film 13 on the back side, the resist 15 is etched and disappears before the etching of the silicon wafer 2 is completed, and the strut is removed. May not be formed. Therefore, the silicon oxide film 13 on the back side is provided as an etching mask.
[0062]
Next, as shown in FIG. 3F, the silicon oxide film 3 in the mask portion 4a is removed. The silicon oxide film 3 can be removed by, for example, wet etching using hydrofluoric acid. By this wet etching, the silicon oxide film 13 on the back side is also removed. As a result, as shown in FIG. 3F, a shape as the stencil mask 1 is formed, and the opening width W of the large diameter portion 6a of the through hole 6 in the silicon nitride film 7 is formed. ₁ Opening width W of aperture 6b having a reduced diameter ₂ Is formed on the silicon layer 4.
[0063]
Next, for example, as shown in FIG. 3 (g), in order to deposit the metal film 10, PVD (hereinafter, referred to as vacuum deposition) such as sputtering or vacuum 3) is performed once, and then, as shown in FIG. 3 (h), vacuum deposition is performed once also from the opposite oblique direction, so that the upper surface of the silicon nitride film 7 and the entire inner wall surface of the passage hole 6 are formed. Next, a metal film 10 is formed to a thickness of 5 to 200 nm. The metal film 10 is formed thicker on the upper surface of the silicon nitride film 7 than on the inner wall surface of the through hole 6 by the vacuum evaporation from the oblique direction, which is good in mechanical strength.
[0064]
As a material, for example, platinum is used. Further, if the adhesion of the foreign matter is equal to or higher than that of platinum, a material other than platinum (for example, at least one of palladium and iridium, an alloy containing these, or a laminate of these metals) may be used. Good. By this oblique deposition, a tapered metal layer 10 along the (111) plane is formed in the aperture 6b of the silicon layer 4, and the wall of the aperture 6b is in contact with the large-diameter wall 6a of the silicon nitride film 7. It is formed in parallel, so that foreign matter hardly adheres to the wall surface of the aperture 6. The angle of the oblique vacuum deposition depends on the distance between the openings of the silicon nitride film 7 and the thickness of the silicon nitride film 7 in the cross-sectional view. Specifically, the smaller the distance between the openings of the silicon nitride film 7, the smaller the inclination angle θ of the vapor deposition is required than the larger the distance between the openings of the silicon nitride film 7. In addition, when the thickness of the silicon nitride film 7 is larger, the inclination angle θ of the vapor deposition needs to be smaller than when the silicon nitride film 7 is thinner. As described above, the distance between the openings of the silicon nitride film 7 is the smallest, and the thicker the silicon nitride film 7 is, the smaller the inclination angle θ of the vapor deposition becomes. In consideration of the above portion, it is preferable to set 0 ° <θ <90 ° and 30 ° ≦ θ ≦ 60 ° in accordance with the necessary condition of the deposition angle θ.
[0065]
The thickness of the metal layer 10 is set within a range in which the strength of the silicon layer 4 is sufficiently reinforced according to the energy of the electron beam when performing the EPL using the stencil mask. For example, in the case of LEEPL in which the acceleration voltage of the electron beam is 2 KeV, it is desirable that the thickness of the metal film 10 be about 20 to 30 nm.
[0066]
Also, the opening width W of the large diameter portion 6a of the passage hole 6 ₁ And the opening width W of the aperture portion 6b ₂ , Ie, (W ₁ -W ₂ ) Changes due to the formation of the metal film 10. Accordingly, the opening width of the large diameter portion after the formation of the metal film 10 is set to W ₁ 'Then W ₁ '-W ₂ <W ₁ -W ₂ And the thickness of the foreign matter attached to the large diameter portion 6a of the passage hole 6 is (W ₁ '-W ₂ ) / 2, W ₂ Since the shape of the foreign matter appears in the opening area and the pattern shape is deformed, the thickness of the metal film 10 is preferably set to a thickness in consideration of the thickness of the foreign matter.
[0067]
Therefore, the thickness of the metal film is
(W ₁ -W ₂ ) / 2- (W ₁ '-W ₂ ) / 2 = (W ₁ -W ₁ ') / 2
It is preferable that the thickness is set to 25 nm or less, assuming that the thickness d of the silicon layer 4 is 50 nm.
[0068]
Next, as shown in FIG. 4 (i), vacuum deposition is also performed on the back side of the stencil mask 1 in the vertical direction using the same material as described above, and the silicon layer 4 exposed in the mask portion 4a region is also formed. A metal film 10 is deposited. The metal film 10 allows the W of the aperture portion 6 to be reduced when performing EPL. ₂ , And foreign matter that has soared up and collides with the transferred portion can be attached. Note that the metal film 19 is also deposited on the lower surface of the strut 12 by this vapor deposition.
[0069]
Next, as shown in FIG. 4J, by removing the metal film 19 on the lower surface of the strut 12, the stencil mask 1 shown in FIG. 1 is formed. However, the metal film 19 may be left for reinforcing the stencil mask 1. By the above-described process, the metal films 10a to 10c continuous from the metal film 10a on the upper surface of the stencil mask 1 to the metal film 10b on the wall surface of the through hole and the reduced metal film 10c on the (111) surface, and the lower surface of the mask portion 4a Thus, a stencil mask 1 having a metal film 10d is obtained, and foreign matter entering the exposure beam passage hole 6 adheres to these metal films 10, so that the shape of the aperture 6b can be maintained.
[0070]
In the above-described process, the silicon nitride film 7 and the silicon layer 4 are etched to form the apertures 6b, and then the silicon wafer 2 is etched to form the struts 12, but on the contrary, the silicon wafer 2 After the struts 12 are formed by etching, the apertures of the large-diameter portions 6a are formed by pattern transfer to the silicon nitride film 7, and the silicon layers 4 are etched to form the aperture portions 6b.
[0071]
FIG. 5A is a schematic cross-sectional view showing a 1: 1 transfer state using the stencil mask 1 of the present embodiment.
[0072]
That is, for example, a negative type electron beam resist film 25 is disposed on an SOI wafer 20 in which a silicon oxide film 23 and a wiring layer 4 made of aluminum are sequentially laminated on a silicon substrate 22, and a gap c (about 50 μm) is formed thereon. The stencil mask 1 is arranged at a distance of and the upper surface is irradiated with the electron beam 18, so that the electron beam 18 passes through the aperture 6 b and the pattern of the stencil mask 1 is formed on the electron beam resist film 25 on the wafer 20. Transcribed.
[0073]
However, fine foreign matters floating in the air in a room or the like enter the exposure beam passage hole 6 with the electron beam 18 and adhere to the inner wall surface of the passage hole 6 formed with high precision. In addition, the adhered material is peeled off, and the pattern shape is deformed by closing an opening or the like, and a pattern defect is easily generated.
[0074]
FIG. 5B shows a state in which such a foreign substance 21 adheres to the metal film 10a on the surface of the stencil mask 1 according to the present embodiment and the metal films 10b and 10c such as the wall surface 6a of the passage hole 6. That is, a large amount of the foreign matter 21 adheres to the metal film 10a on the surface on which the foreign matter 21 is easily deposited, and the foreign matter 21 that has entered the through hole 6 is largely attached to the vicinity of the entrance even in the large diameter portion 6a of the through hole 6 having a large surface area, and is reduced. Few reach the inclined portion of the aperture 6b. For this reason, it is possible to avoid sticking to the wall surface of the aperture portion 6b formed with high precision, and to maintain the pattern. The foreign matter 21 that has passed through the aperture 6b temporarily adheres to the metal film 10d on the lower surface of the mask 4a while floating inside.
[0075]
As described above, the metal film 10 to which foreign matter or the like easily adheres is formed almost continuously from the surface of the stencil mask 1 to the entire inner wall surface of the passage hole 6 so that foreign matter existing in the air can be removed from the metal film 10. It is a remarkable feature of the stencil mask 1 of the present embodiment that a foreign matter removing measure can be performed by adhering to the stencil mask 1 and that the pattern shape of the aperture 6b is maintained and the pattern is prevented from being defective.
[0076]
By forming the metal film 10 in this manner, in the invention of the prior application, the opening width W of the large-diameter portion of the passage hole 6 is increased. ₁ , The aperture portion 6b is precisely reduced W ₂ In addition to the effect of being formed in ₂ Can be maintained without deforming the surface.
[0077]
According to the present embodiment, a silicon nitride film 7 is laminated as a membrane support layer on an SOI wafer 5 having a (100) plane parallel to the film surface and having a silicon layer 4 as a membrane. The opening width W of the large diameter portion 6a as the passage hole 6 ₁ Is formed and wet etching is performed using a KOH solution with the silicon nitride film 7 as a mask, so that a through hole 6 formed in the silicon layer 4 is formed on the (111) plane due to a difference in etching rate. Therefore, the aperture portion 6b which is reduced with a certain angle (54.7 °) is formed with the opening width W. ₂ And a mask portion 4a is formed.
[0078]
Subsequently, after the silicon wafer 2 and the silicon oxide film 3 on the back side of the SOI wafer 5 are removed so as to correspond to the mask portion 4a to form struts 12, the surface of the silicon nitride film 7 and the inside of the through holes 6 are formed. Almost the entire wall surface and the lower surface of the silicon layer 4 are formed by oblique vacuum deposition of a metal film 10 made of platinum, and the stencil mask 1 of the present embodiment is formed.
[0079]
As a result, the opening width W of the aperture portion 6b ₂ Is the opening width W of the large diameter portion 6a. ₁ In addition to having the same effect as the invention of the prior application, foreign matter easily adheres to the metal film 10 when performing EPL using this stencil mask 1 The foreign matter 21 in the air that enters the passage hole from the front surface adheres to the surface and the wall surface of the passage hole near the surface, and does not adhere to the opening of the reduced aperture portion 6b. And the mechanical strength of the exposure mask is increased by the conductive film, so that a fine pattern can be transferred with high accuracy, and a highly reliable semiconductor device can be manufactured.
[0080]
The above-described embodiment can be variously modified based on the technical idea of the present invention.
[0081]
For example, in the embodiment, the strut 12 is provided as a supporting portion on the back surface side of the stencil mask 1. However, as a means for supporting the membrane 4, only the silicon nitride film 7 on the membrane 4 is made as thick as possible. As a result, the struts 12 may not be provided or may be thinned by polishing. Thereby, when performing EPL, the gap between the lower surface of the aperture portion 6b and the transfer receiving surface is narrowed, so that the transfer accuracy can be further improved.
[0082]
Further, when forming the metal film 10 on the inner wall surface or the like of the through hole 6, the metal film 10 is formed by performing vacuum deposition obliquely from the target direction. However, the metal film 10 is not formed individually from each angle. Alternatively, the metal particles may be made to fly continuously from the direction described above to another direction, and the flying locus may be formed in a fan shape.
[0083]
Further, the metal film 10 may be formed by plating (for example, through-hole plating technology) instead of oblique deposition.
[0084]
In the above-described embodiment, a stencil mask for EPL other than LEEPL such as PREVAIL, a mask for a variable-shaped electron beam direct drawing machine, a mask for ion beam lithography, a mask for X-ray lithography, etc. Can be applied to other masks. Further, in addition to lithography, the present invention can be applied to a mask for locally irradiating charged particles such as ion implantation.
[0085]
Effects of the Invention
As described above, according to the present invention, the wall surface of the exposure beam passage hole formed in the single crystal film is formed flat, and the passage hole in the single crystal film is controlled and reduced at a fixed angle, so that The width of the passage hole is formed with high precision. In addition, since at least substantially the entire inner wall surface of the exposure beam passage hole and the one surface are covered with the conductive film, foreign matter entering the passage hole is reduced by the one surface and the inner wall surface of the passage hole. Attached to the conductive film, it does not adhere to the pattern opening formed by the reduced passage hole, and the shape of the pattern opening can be maintained, and the mechanical strength of the exposure mask is increased by the conductive film. Transfer can be performed with high accuracy, and a semiconductor device can be manufactured with high reliability.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a stencil mask according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view showing a manufacturing process of the stencil mask.
FIG. 3 is a schematic sectional view showing a manufacturing process of the stencil mask.
FIG. 4 is a schematic sectional view showing a manufacturing process of the stencil mask.
5A and 5B show the use state of the stencil mask, FIG. 5A is a schematic sectional view, and FIG. 5B is an enlarged view of a part of FIG.
6A and 6B show a stencil mask according to the invention of the prior application, wherein FIG. 6A is a schematic cross-sectional view, FIG. 6B is an enlarged view of a part of FIG. 6A, and FIG.
FIG. 7 is a schematic sectional view of a stencil mask according to a conventional example.
FIG. 8 is a schematic sectional view of a mask using a pellicle.
[Explanation of symbols]
1, 1A: stencil mask, 2, 22: silicon wafer,
3, 13, 23: silicon oxide film, 4: silicon layer (membrane),
4a: mask portion, 5, 20: SOI wafer, 6: through hole, 6a: large diameter portion,
6b: aperture portion, 7: silicon nitride film, 8: surface (one surface),
9: back surface (other surface), 10: metal film, 11: thin film, 12: strut,
14, 15, 25: resist film, 18: electron beam, 21: foreign matter,
24 ... Aluminum, W ₁ , W ₂ … Opening width

Claims (19)

In an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern,
A single crystal film having a first lattice plane parallel to the film surface;
At least, the thin film including the single crystal film, and a support layer that supports the single crystal film on the one surface side,
The exposure beam passage hole formed in the thin film,
A second lattice plane that constitutes a wall surface of the exposure beam passage hole of the single crystal film, and reduces the exposure beam passage hole from the one surface side to the other surface side in the single crystal film;
An exposure mask, comprising: a conductive film covering at least substantially the entire inner wall surface of the exposure beam passage hole and the one surface. The exposure mask according to claim 1, wherein the other surface side of the single crystal film is also covered with a conductive film. The exposure mask according to claim 1, wherein the other surface side of the single crystal film is supported by a support. The exposure mask according to claim 1, wherein the first lattice plane of the single crystal film is a (100) plane or a (110) plane, and the second lattice plane is a (111) plane. 2. The exposure mask according to claim 1, wherein the conductive film is made of at least one of platinum, palladium, and iridium having foreign substance adhesion, an alloy containing these, or a laminate of these metals. The exposure mask according to claim 1, wherein the exposure beam is a charged particle beam. In a method of manufacturing an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern,
A support layer for supporting the single crystal film on the one surface side on a single crystal film having a first lattice plane parallel to the film surface and a second lattice plane intersecting the first lattice plane Forming a;
Forming a first passage hole corresponding to the exposure beam passage hole in the support layer;
Etching the single crystal film through the first passage hole to reduce the exposure beam passage hole from the one surface side to the other surface below the first passage hole; Forming a second passage hole comprising a lattice plane of
At least substantially covering the entire inner wall surface of the exposure beam passage hole formed by the first passage hole and the second passage hole and the one surface with a conductive film. A method for manufacturing an exposure mask. The method for manufacturing an exposure mask according to claim 7, wherein the conductive film is adhered by causing deposited particles to fly from different directions with respect to the exposure beam passage hole. The method for manufacturing an exposure mask according to claim 7, wherein a conductive film is also attached to the other surface side of the single crystal film by flying deposited particles. The method for manufacturing an exposure mask according to claim 8, wherein the deposition particles are attached by sputtering or vapor deposition. The method of manufacturing an exposure mask according to claim 7, wherein the first passage hole is formed by dry etching, and the second passage hole is formed by wet etching. The exposure mask according to claim 7, wherein the other surface side of the single crystal film is supported by a support portion, and a third passage hole larger than the mask portion including the exposure beam passage hole is formed in the support portion. Production method. The method for manufacturing an exposure mask according to claim 12, wherein a conductive film is attached by flying the deposited particles from the other surface side of the support portion. The method according to claim 7, wherein the first lattice plane of the single crystal film is a (100) plane or a (110) plane, and the second lattice plane is a (111) plane. The method for manufacturing an exposure mask according to claim 7, wherein the conductive film is formed of at least one of platinum, palladium, and iridium having foreign substance adhesion, an alloy containing these, or a laminate of these metals. The method according to claim 7, wherein the exposure beam is a charged particle beam. A method for manufacturing a semiconductor device using an exposure mask in which an exposure beam passage hole penetrating from one surface side to the other surface side is formed in a predetermined pattern,
A single crystal film having a first lattice plane parallel to the film surface;
At least, the thin film including the single crystal film, and a support layer that supports the single crystal film on the one surface side,
The exposure beam passage hole formed in the thin film,
A second lattice plane that constitutes a wall surface of the exposure beam passage hole of the single crystal film, and reduces the exposure beam passage hole from the one surface side to the other surface side in the single crystal film;
At least the photosensitive layer on the semiconductor substrate is exposed in a predetermined pattern using an exposure mask having a conductive film covering at least the entire inner wall surface of the exposure beam passage hole and the one surface. And a method of manufacturing a semiconductor device. A method for manufacturing a semiconductor device according to claim 17, wherein the exposure mask is manufactured by the manufacturing method according to any one of claims 8 to 16. The method of manufacturing a semiconductor device according to claim 17, wherein an etching mask is formed by developing the photosensitive layer exposed to the predetermined pattern, and the layer to be etched on the semiconductor substrate is etched with the etching mask.

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