JP2004111704A - Manufacturing method for membrane mask and membrane mask using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a membrane mask for simultaneously increasing precision in the dimensions of a mask pattern and precision in a transfer pattern. <P>SOLUTION: A diamond film, whose surface is polished, is used as the membrane of the membrane mask for circuit pattern transfer and is etched for forming a pattern. Roughness on the surface of the diamond film is 0.1 to 10 nm and manufacture is made, by using a heavy metal layer as the etching mask for etching the diamond film. Additionally, a membrane mask can be manufactured, without removing the heavy metal layer, after etching the diamond film. Furthermore, a metal film or a silicon carbide film can be used, in place of the diamond mask. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a membrane mask and a membrane mask using the method. More specifically, the present invention relates to a method for producing a membrane mask, for example, an X-ray mask or an electron beam mask, used in an exposure step for forming a circuit pattern of a device, and a membrane mask using the production method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a transfer mask used for an X-ray mask or an electron beam mask, there is a transfer mask in which an opening is formed in a thin film portion of a carbon-based material supported by a support frame (for example, see Patent Document 1).
[0003]
This transfer mask is manufactured as follows. First, a diamond film having a thickness of 5 μm is formed on a double-side polished silicon substrate by ECP-CVD. Next, after forming a SiO ₂ film with a thickness of 1000 Å on the diamond film, a resist is applied on the SiO ₂ film and is patterned to form a resist pattern. Next, using this resist pattern as a mask, the SiO ₂ film is etched to form a SiO ₂ pattern.
[0004]
Then, using the SiO ₂ pattern as a mask, the diamond film is etched using oxygen gas as an etching gas to form a predetermined opening pattern in the diamond film.
[0005]
Next, a SiO ₂ film is formed on the back surface side of the silicon substrate, and this is etched to form a window pattern on the SiO ₂ film.
[0006]
Then, using this back side SiO ₂ film as a mask, the silicon in the exposed window area is etched from the back side by wet etching to form a window. Thus, a silicon support frame and a diamond thin film supported by the silicon support frame are formed.
[0007]
Next, after the unnecessary SiO ₂ films on the front and back are removed, a metal film is formed on the front and back of the mask to manufacture a transfer mask.
[0008]
As the thin film portion of the carbon-based material, a carbon-based film made of carbon, DLC (diamond-like carbon), graphite, or the like can be used in addition to the diamond film.
[0009]
An opening pattern is formed by dry etching of a carbon-based film using oxygen as a main gas. At this time, instead of SiO ₂ , an inorganic material such as SiC, Si ₃ N ₄ , sialon (a composite mixture of Si and Al), SiON, or an organic material such as a resist or a photosensitive film is used as an etching mask layer. Metal materials such as metals such as titanium, aluminum, tungsten, zirconium, chromium, and nickel, alloys containing these metals, and metal compounds of these metals or alloys with oxygen, nitrogen, and carbon are used.
[0010]
Further, instead of the front and back surfaces of the transfer mask, a metal film can be formed on the irradiation surface or the entire surface of the formed opening pattern. Examples of the metal film include iridium (Ir), tantalum (Ta), tungsten (W), molybdenum (Mo), gold (Au), platinum (Pt), and silver (Ag).
[0011]
[Patent Document 1]
JP-A-10-189435
[Problems to be solved by the invention]
However, in a conventional transfer mask, although a diamond film is used as a carbon-based film, irregularities are naturally generated on the surface of the diamond film. This unevenness does not cause any problem when patterning a large pattern. On the other hand, when patterning a fine pattern, there is a problem that dimensional accuracy is reduced. This is because the etching mask that has entered the concave portion of the diamond film tends to remain when the etching mask is patterned. As a result, when the diamond film is etched with oxygen, the etching mask that remains in the concave portion causes a needle-like shape when the diamond film is etched. This is because a residue of a diamond film is generated or an edge roughness of a pattern is increased, thereby lowering dimensional accuracy. Therefore, when the transfer is performed using such a mask, there is a problem that the dimensional accuracy of the transfer pattern is reduced and the device accuracy is deteriorated.
[0013]
Further, since the selection of an etching mask when etching the diamond film is poor, the diamond film is not accurately etched, and as a result, the dimensional accuracy of the transfer pattern is reduced.
[0014]
In addition, since the diamond film has poor electrical conductivity, in the case of an electron beam mask using the diamond film, charge-up occurs on the diamond film, and as a result, the electron beam is bent, and the accuracy of the transfer pattern is reduced. There's a problem. In order to solve the problem, in the conventional transfer mask, the metal film is formed on the front and back surfaces, the irradiation surface, or the entire surface of the formed opening pattern. In this case, the metal film is also formed on the side surface of the opening pattern. In addition, there is a problem that the size of the opening is reduced, the dimensional accuracy of the mask is reduced, and the dimensional accuracy of the transfer pattern is reduced.
[0015]
Further, in order to prevent charge-up of the membrane, silicon carbide is mentioned as a conductive membrane, but it is difficult to etch this membrane with high accuracy. As a result, there is a problem that the dimensional accuracy of the transfer pattern is reduced.
[0016]
In view of the circumstances described above, an object of the present invention is to provide a method of manufacturing a membrane mask capable of improving the dimensional accuracy of a mask pattern and improving the accuracy of a transfer pattern, and to provide a membrane mask using the manufacturing method. I do.
[0017]
[Means for Solving the Problems]
The method of manufacturing a membrane mask of the present invention is characterized in that a diamond film whose surface is polished is used as a membrane of a membrane mask for transferring a circuit pattern, and the diamond film is etched to form a pattern.
[0018]
Further, a method of manufacturing a membrane mask of the present invention is characterized in that a metal film is used as a membrane of a membrane mask for transferring a circuit pattern, and the metal film is etched to form a pattern.
[0019]
Further, the method for producing a membrane mask of the present invention uses a silicon carbide film having a polished surface as a membrane of a membrane mask for transferring a circuit pattern, and uses a film containing chromium as an etching mask for the silicon carbide film. The pattern is formed by etching a silicon carbide film.
[0020]
Further, the membrane mask of the present invention is a membrane mask for transferring a circuit pattern, using a membrane made of a silicon carbide film whose surface is polished, and using a film containing chromium as an etching mask on the silicon carbide film, It is characterized in that a pattern is formed by etching a silicon carbide film.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, a pattern of a membrane mask can be accurately etched. By using this mask, charge-up can be prevented in the case of electron beam transfer. Therefore, when transfer is performed using this mask, the accuracy of the transfer pattern can be improved. As a result, a highly accurate device can be manufactured with high yield, and the cost can be reduced.
[0022]
Hereinafter, a method for producing a membrane mask of the present invention and a membrane mask using the method will be described with reference to the accompanying drawings.
[0023]
Embodiment 1
1 to 3 are cross-sectional views illustrating a method for manufacturing a membrane mask according to Embodiment 1 of the present invention.
[0024]
The membrane mask of the present invention is a membrane mask for transferring a manufacturing circuit pattern, and can be applied to a mask used for X-ray exposure or electron beam drawing exposure. As shown in FIG. 1, a mask used for X-ray exposure includes a silicon substrate 1 and a diamond film formed on the silicon substrate 1 and having a surface polished so as to have a surface roughness of 0.1 to 10 nm. 5 and a heavy metal layer (hereinafter, referred to as a heavy metal absorber) 4 also serving as an etching mask and an X-ray absorber for the diamond film 5, and the etching of the heavy metal absorber 4 and the diamond film 5 is stopped halfway. A predetermined hole 11 (non-through hole) pattern is formed. As the heavy metal absorber 4, for example, tungsten or tantalum can be used. This mask can be used as an electron beam mask of a type that transmits highly accelerated electrons. This mask can also be used as an X-ray phase shift mask. In this case, the amount of X-ray phase shift can be changed by the amount of etching of the diamond film 5. As a result, a fine pattern can be transferred.
[0025]
On the other hand, as shown in FIG. 2, the mask used for the electron beam lithography exposure includes the silicon substrate 1, the diamond film 5 whose surface is polished, the etching mask of the diamond film 5, and the absorption of the electron beam. The heavy metal absorber 4 also serves as a body, and the heavy metal absorber 4 and the diamond film 5 are etched to the end to form a predetermined through-hole 21 pattern.
[0026]
In the first embodiment, there is no residue, and the diamond film can be etched accurately. In this case, when the surface roughness is set to 0.1 to 10 nm, the dimensional accuracy of the mask pattern is further improved, and the device can be applied to a device for pattern drawing of 100 nm or less. The surface roughness is preferably closer to zero, but it cannot actually be zero, so the practical lower limit is about 0.1 nm. When the etching of the diamond film is stopped halfway, the phase of the X-ray can be controlled by the etching amount of the diamond film. As a result, transfer of the fine pattern becomes easy. Further, when a heavy metal absorber is used as an etching mask used for etching a polished diamond film, the heavy metal absorber is not etched by oxygen, so that a selective ratio with the diamond film at the time of etching can be ensured, and accuracy can be improved. Good etching becomes possible. The ordinary etching mask must be removed after etching, but the heavy metal absorber can be left as it is after etching the diamond film because it has excellent electron and X-ray stopping power. Furthermore, since charge-up due to electron beams can be prevented, there is no need to remove the etching mask after etching the diamond film and form a metal film for preventing charge-up.
[0027]
Next, an example of a method for manufacturing a membrane mask when a diamond film is used as a membrane will be described. As shown in FIG. 3A, first, a diamond film was formed on a silicon substrate (not shown) by a CVD method or the like. After that, the surface of the diamond film was polished to obtain a diamond film 5. Here, when polishing is not performed as described later, the surface of the diamond has irregularities of about 0.1 μm, and it is difficult to form a fine pattern. Therefore, it is preferable to perform polishing so as to have a surface roughness of 10 nm or less.
[0028]
Next, a heavy metal absorber 4 for X-ray and electron beam absorption was formed. The heavy metal absorber 4 is formed by sputtering tungsten or tantalum, for example. After that, an etching mask 6 for patterning heavy metals was formed thereon. As the etching mask 6, for example, chromium or chromium nitride can be used. Then, a resist 7 was applied, and a resist pattern was formed by an electron beam lithography apparatus.
[0029]
Next, as shown in FIG. 3B, the etching mask 6 was etched with a mixed gas of chlorine and oxygen. After that, in the present embodiment, a resist removing step is included, but in the present invention, the resist removing step can be omitted.
[0030]
Next, as shown in FIG. 3C, the heavy metal absorber 4 was etched using the etching mask 6. For example, when tungsten is used as heavy metal absorber 4, etching is performed with SF ₆ —CHF ₃ , and when tantalum is used, etching is performed with chlorine gas. After that, in the present embodiment, the etching mask 6 is removed, but in the present invention, such a removing step can be omitted.
[0031]
Then, as shown in FIG. 3D, the diamond film 5 was etched with oxygen gas using the heavy metal absorber 4 as a mask. At this time, the etching of the diamond film 5 was stopped halfway. Further, the etching of the diamond film 5 was performed to the end to form a through hole.
[0032]
Thus, a membrane mask for X-ray lithography and a membrane mask for electron beam lithography were manufactured.
[0033]
Comparative Example Next, the case where the dimensional accuracy of the membrane mask is reduced when the surface of the diamond film is not polished will be described. As shown in FIGS. 4 (a) and 5 (a), the surface of the diamond film 2 formed on the silicon substrate (not shown) has irregularities. When a film is formed and a resist pattern is formed, scum of the resist 7 tends to remain in the concave portion. In FIG. 4A, reference numeral 4 denotes a heavy metal absorber, and reference numeral 6 denotes an etching mask.
[0034]
Then, as shown in FIGS. 4B and 5B, when the etching mask 6 was patterned, the etching mask 6 remained on the heavy metal absorber 4.
[0035]
Then, as shown in FIGS. 4C and 5C, when the heavy metal absorber 4 was etched, the heavy metal absorber 4 remained in the concave portion on the surface of the diamond film 2.
[0036]
Then, as shown in FIGS. 4D and 5D, when the diamond film 2 was etched, residues were generated, and edge roughness of the pattern was generated.
[0037]
For this reason, the dimensional accuracy of the membrane mask was reduced.
[0038]
This is the rate of decrease in dimensional accuracy. For example, if there is a concave portion of 10 nm on the surface of the diamond film, a resist or an etching mask is likely to remain there, so that the edge roughness generally has a size of about 10 nm. Become. In X-ray exposure and electron beam exposure, pattern writing of 100 nm or less is mainly considered, and in this case, the dimensional accuracy is 10% of 100 nm, so that if there is an edge roughness exceeding 10 nm, the device will malfunction. Cheap. Therefore, the surface roughness of the diamond film is 0.1 to 10 nm.
[0039]
Embodiment 2
In the second embodiment, a membrane mask using a metal film as a membrane can be used instead of the diamond film whose surface is polished in the first embodiment. In such a case, the metal film is manufactured by bonding a metal film thinned by rolling or the like to a silicon wafer or the like and then patterning the metal film, and finally dissolving the silicon, or bonding to a donut-shaped silicon substrate, There are a method in which a membrane is formed beforehand, and a method in which a silicon wafer is formed by sputtering or CVD. In the second embodiment, an etching mask is formed after forming a metal film by any one of the above methods. Next, a resist is applied and the metal film is patterned to produce a membrane mask.
[0040]
In the second embodiment, as in the first embodiment, the dimensional accuracy of the mask pattern can be improved, and the accuracy of the transfer pattern can be improved. As a result, a highly accurate device can be manufactured with high yield, and the cost can be reduced.
[0041]
Embodiment 3
In the third embodiment, a membrane mask using a silicon carbide (SiC) film as a membrane can be used instead of the diamond film whose surface is polished in the first embodiment. In the third embodiment, first, silicon carbide is formed on a silicon substrate by CVD. After that, the surface is polished so as to be smooth, and an etching mask containing chromium (Cr) is formed. Next, the resist is patterned, and the film containing chromium is etched by chlorine-oxygen gas. Then, after etching the silicon carbide film with a fluorine-based gas, for example, SF ₆ or the like, a membrane mask is manufactured.
[0042]
Here, in the case where a silicon carbide film is used, charge-up during electron beam exposure is reduced due to conductivity, but it is difficult to accurately etch the silicon carbide film. However, when a film containing chromium is used, chromium is generally etched using a chlorine-oxygen gas, but is not etched at all by a fluorine-based gas. On the other hand, the silicon carbide film is easily etched with a fluorine-based gas, but is not etched at all with a chlorine-based gas.
[0043]
Since the silicon carbide film has such different characteristics, it is possible to obtain a large selection ratio, for example, about 10, when etching the silicon carbide film. As a result, the third embodiment differs from the first embodiment with respect to the first embodiment. Similarly, the dimensional accuracy of the mask pattern can be improved, and the accuracy of the transfer pattern can be improved. As a result, a highly accurate device can be manufactured with high yield, and the cost can be reduced.
[0044]
Embodiment 4
When the membrane is patterned using the diamond film, the metal film or the silicon carbide film whose surface is polished, distortion occurs due to the stress remaining on the membrane. Approximately, when the thickness is 0.5 μm and the stress is 10 MPa, a strain of about 10 nm is generated. Therefore, if the distortion is measured with the first mask and the opposite amount of the distortion is corrected with the second mask, the distortion due to the second mask is theoretically within the drawing accuracy of the electron beam exposure machine. However, actually, since the stress of the first mask is not the same as the stress of the second mask, a correction difference due to the second mask occurs. This depends on the reproducibility of the stress of the two masks. Although it depends on the film forming method, the reproducibility of the stress is generally about 10% of the stress value. For example, if the stress is 100 MPa, the reproducibility is ± 10 MPa, so that the reproducibility is 90 to 110 MPa.
[0045]
Here, in the case of a 100 nm pattern targeted by electron beam drawing or X-ray exposure, a predetermined mask accuracy is about 1/3 of that, so that a position accuracy of about 30 nm is required. That is, since the reproducibility is ± 30 (3 × 10) MPa, when the thickness of the membrane is 0.5 μm, a membrane stress of 300 (3 × 100) MPa or less is required. Since this stress value changes depending on the thickness of the membrane, for example, if the membrane thickness is 1 μm, 150 (0.5 / 1 × 300) MPa, if the membrane thickness is 2 μm, 75 (0.5 / 2 × 300) MPa, If it is 0.3 μm, it will be 500 (0.5 / 0.3 × 300) MPa. That is, the stress value (MPa) of the membrane = 150 ÷ the thickness (μm) of the membrane. With this stress value or less, a highly accurate mask can be manufactured.
[0046]
Further, when the stress of the membrane is reduced, distortion during patterning of the mask is reduced, and a highly accurate mask can be manufactured. Therefore, the accuracy of the transfer pattern can be improved.
[0047]
Embodiment 5
In an etching mask used for etching a diamond or silicon carbide film, the smaller the stress value, the smaller the distortion. Approximately, when the thickness is 0.5 μm and the stress is 10 MPa, a strain of about 10 nm is generated. In theory, it is theoretically possible to correct the distortion by electron beam lithography, but it is difficult to correct the distortion of the membrane at the same time. Needs to be dealt with. In that case, in order to reduce the distortion to 30 nm or less, the stress of the etching mask needs to be 30 MPa or less. Since this also depends on the film thickness, for example, if the thickness of the etching mask is 0.1 μm, the stress is desirably 150 MPa or less. That is, the stress value (MPa) of the etching mask = 15 ÷ the thickness (μm) of the etching mask. With this stress value or less, a highly accurate mask can be manufactured.
[0048]
In addition, when the stress of the etching mask is reduced, distortion during patterning of the mask is reduced, and a highly accurate mask can be manufactured. Therefore, the accuracy of a transfer pattern can be improved.
[0049]
【The invention's effect】
As described above, according to the first aspect of the present invention, a diamond film whose surface is polished is used as a membrane of a membrane mask for transferring a circuit pattern, and the diamond film is etched to form a pattern. The pattern of the mask can be accurately etched. Further, by using this mask, charge-up can be prevented in the case of electron beam transfer. Therefore, when transfer is performed using this mask, the accuracy of the transfer pattern can be improved. As a result, a highly accurate device can be manufactured with high yield, and the cost can be reduced.
[0050]
According to the fifth aspect of the present invention, since a pattern is formed by etching a metal film using a metal film as a membrane of a membrane mask for transferring a circuit pattern, it is possible to form a pattern with high accuracy. In addition, the membrane does not charge up during exposure, and a pattern with high dimensional accuracy can be formed. Further, when manufacturing a mask, it is not necessary to form a metal film for preventing charge-up, so that the process is simplified and the cost can be reduced.
[0051]
Further, according to the present invention, a silicon carbide film whose surface is polished is used as a membrane of a membrane mask for transferring a circuit pattern, and a film containing chromium is used as an etching mask of the silicon carbide film. Thus, since the silicon carbide is etched to form a pattern, a large selectivity can be obtained when etching the silicon carbide, thereby improving the dimensional accuracy of the mask pattern and the accuracy of the transfer pattern. Can be. As a result, a highly accurate device can be manufactured with high yield, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a membrane mask obtained by a method for manufacturing a membrane mask according to Embodiment 1 of the present invention.
FIG. 2 is a sectional view of another membrane mask according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a method for manufacturing a membrane mask according to the first embodiment.
FIG. 4 is a cross-sectional view illustrating a comparative example.
FIG. 5 is a plan view illustrating a comparative example.
[Explanation of symbols]
Reference Signs List 1 silicon substrate, uneven diamond film, heavy metal layer (heavy metal absorber), surface-polished diamond film, 6 etching mask, 7 resist, 11 holes, 21 through holes.

Claims (9)

A method for producing a membrane mask, wherein a diamond film whose surface is polished is used as a membrane of a membrane mask for transferring a circuit pattern, and the diamond film is etched to form a pattern. The method for producing a membrane mask according to claim 1, wherein the surface roughness of the diamond film is 0.1 to 10 nm. 2. The method according to claim 1, wherein a heavy metal layer is used as an etching mask for etching the diamond film. The method according to claim 3, wherein the heavy metal layer is not removed after etching the diamond film. A method of manufacturing a membrane mask for forming a pattern by using a metal film as a membrane of a membrane mask for transferring a circuit pattern and etching the metal film. A silicon carbide film having a polished surface is used as a membrane of a membrane mask for transferring a circuit pattern, and a pattern containing chromium is used as an etching mask for the silicon carbide film to form a pattern by etching the silicon carbide film. Manufacturing method of membrane mask. 7. The method for producing a membrane mask according to claim 6, wherein the silicon carbide has a surface roughness of 0.1 to 10 nm. A membrane mask for transferring a circuit pattern, using a membrane made of a silicon carbide film having a polished surface, using a film containing chromium as an etching mask for the silicon carbide film, and etching the silicon carbide film. A membrane mask on which a pattern is formed. The membrane mask according to claim 8, wherein the silicon carbide has a surface roughness of 0.1 to 10 nm.

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