JP3809754B2 - Method for manufacturing transfer mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transfer mask used for exposure of a charged beam such as an electron beam or an ion beam, and a method for manufacturing the transfer mask.
[0002]
[Prior art]
Miniaturized circuits and structures typified by semiconductor integrated circuit patterns are still being miniaturized, and the complexity of patterns tends to increase further. In order to cope with this, pattern formation by charged beam exposure has attracted attention in recent years, and two single crystal silicon wafers having a plane orientation of (100) are bonded to each other with a silicon oxide film in this transfer mask for charged beam exposure. In many cases, an SOI (Silicon on Insulator: silicon / silicon oxide film / silicon structure) substrate is used.
[0003]
The transfer mask manufacturing process can be broadly classified into two processes: a process of forming a transfer mask pattern on the upper single crystal silicon wafer and a process of forming an opening in the lower single crystal silicon wafer to be a silicon support substrate. When the transfer mask pattern is formed on the upper single crystal silicon wafer, the silicon oxide film 3 is normally used as shown in FIG. 3 by using the etching selectivity between the upper single crystal silicon wafer 1 and the silicon oxide film 3. A transfer mask pattern was formed by dry etching using as an etching stopper.
[0004]
However, as shown in FIG. 2, when the etching reaches the silicon oxide film 3 and the silicon oxide film 3 as an insulating film is exposed, the silicon oxide film 3 is charged up by the incident cations 20 and incident later. A phenomenon in which the orbit of the cation 20 is bent near the bottom of the pattern and etching proceeds in the lateral direction, so-called notching occurs.
[0005]
In the vicinity of the fine pattern, electrons are decelerated by the negative potential from the lower side of the lower single crystal silicon wafer, and thus are captured in the vicinity of the resist 8, but the cation 20 is guided to the negative potential and reaches the bottom of the pattern. For this reason, charge separation occurs between the resist and the bottom of the pattern as shown in FIG. 2, and the trajectory of the cation 20 reaching the vicinity of the bottom of the pattern is bent.
When the above notching occurs, the miniaturization of the pattern is progressing, and there is a problem that the notching progresses to the adjacent pattern and the pattern is destroyed.
[0006]
In order to suppress this notching, ultra-fine processing technology (edited by Tokuyama Satoshi, Ohm Co., Ltd.) uses a thick side wall protective film to suppress the arrival of ions whose trajectories are bent and the plasma density. It is written that lowering is effective. However, if further miniaturization proceeds and the pattern groove becomes narrower in the future, it will become more difficult to form the sidewall protective film, and the charge separation will become more prominent.
Further, as the pattern becomes finer, the requirement for dimensional accuracy becomes stricter, and there is a problem of resist deformation due to the temperature rise of the substrate to be processed during dry etching.
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and its purpose is to provide a transfer mask manufactured using an SOI substrate in which two single crystal silicon wafers are bonded with a silicon oxide film. Method of manufacturing a transfer mask for charged beam exposure with no defects and extremely high transfer accuracy by suppressing notching and substrate temperature rise when processing a transfer mask pattern by dry etching using a silicon oxide film as an etching stopper And providing a transfer mask.
[0008]
[Means for Solving the Problems]
The present invention relates to a method of manufacturing a transfer mask using an SOI substrate in which two single crystal silicon wafers are bonded with a silicon oxide film, and after forming an opening in a lower single crystal silicon wafer to be a support substrate, After removing the silicon oxide film, and then forming a conductive film on at least the surface of the upper single crystal silicon wafer facing the opening and the bottom surface of the lower single crystal silicon wafer, a transfer mask is formed on the upper single crystal silicon wafer. A method of manufacturing a transfer mask, comprising at least a step of forming a pattern and then removing the conductive film .
[0009]
In the present invention, the conductive film includes at least one of aluminum, titanium, chromium, nickel, copper, zirconium, niobium, molybdenum, palladium, silver, tantalum, tungsten, osmium, platinum, and gold. The method of manufacturing a transfer mask according to claim 1.
[0012]
A feature of the present invention is that after an opening is formed in the lower single crystal silicon wafer to be a support substrate, the silicon oxide film is removed, and then at least the surface of the upper single crystal silicon wafer facing the opening is electrically conductive. After forming the film, the method includes a step of forming a transfer mask pattern on the upper single crystal silicon wafer.
Thus, by using the conductive film as an etching stopper for dry etching of the upper single crystal silicon wafer, it is possible to reduce the charge-up of the etching stopper that causes notching. Further, by bringing the substrate holder of the etching apparatus into contact with the conductive film, the temperature rise of the upper single crystal silicon wafer during dry etching can be suppressed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
A method for manufacturing a transfer mask and a transfer mask according to the present invention will be described based on embodiments thereof. FIG. 1A to FIG. 1F are explanatory views showing, in partial cross section, an example of a transfer mask manufacturing method according to the present invention.
First, as shown in FIG. 1A, a wet etching protective film 5 is formed on the entire surface of an SOI substrate 4 in which two single crystal silicon wafers 1 and 2 are bonded with a silicon oxide film 3, and a resist (not shown) is formed. The opening pattern 6 is formed in the wet etching protective film 5 on the lower single crystal silicon wafer 2 side by dry etching.
[0014]
Next, as shown in FIG. 1B, the wet etching protective film 5 in which the opening pattern 6 is formed is used as an etching mask until etching reaches the silicon oxide film 3, and the lower single crystal silicon wafer 2 is etched. An opening 6a is formed in the substrate.
Here, although wet etching is used as a method of forming the opening 6a in the lower single crystal silicon wafer 2 in FIG. 1, dry etching, ultrasonic processing, sandblasting, or the like can also be used.
[0015]
Subsequently, as shown in FIG. 1C, after the etching protective film is removed, the silicon oxide film 3 exposed in the opening 6a of the lower single crystal silicon wafer 2 is removed by wet etching, and the upper part is opened in the opening 6a. One surface of the single crystal silicon wafer is exposed.
Next, as shown in FIG. 1 (d), a conductive film 7 is formed on the surface facing the opening 6a and the bottom surface of the lower single crystal silicon wafer 2a where the opening 6a is formed, and then the upper unit. A resist 8 on which a transfer mask pattern 9 is formed is provided on the crystalline silicon wafer 1 side. The conductive film 7 may be formed at least on the surface of the upper single crystal silicon wafer facing the opening 6a.
[0016]
The conductive film 7 is made of aluminum, titanium, chromium, nickel, copper, zirconium, niobium, molybdenum, palladium, silver, tantalum, tungsten, osmium, platinum, gold metal, an alloy containing these metals, or these metals or alloys. And metal compounds of oxygen, nitrogen, carbon, and the like can be used. As a method for forming the conductive film, a sputtering method, a CVD method, a vapor deposition method, a plating method, an electrodeposition method, an ion plating method, or the like can be used.
In order to form the transfer mask pattern 9 on the resist 8, direct electron beam drawing using an electron beam resist, stepper exposure using a photoresist, or the like can be suitably used.
[0017]
Next, as shown in FIG. 1E, the transfer mask pattern 9 is formed on the upper single crystal silicon wafer by dry etching using the resist 8 on which the transfer mask pattern 9 is formed as an etching mask.
Here, when dry etching of the upper single crystal silicon wafer, if the resist resistance is insufficient, inorganic materials such as silicon oxide film, silicon nitride film, silicon carbide film, chromium, tungsten, tantalum, titanium, A metal such as nickel or aluminum, an alloy containing these metals, or a metal compound of these metals or alloys with oxygen, nitrogen, carbon, or the like is used as an etching mask. These etching masks can be formed by various thin film forming methods. For example, there are forming methods such as sputtering, CVD, and vapor deposition.
[0018]
For dry etching, the dry etching method and conditions are not particularly limited. Examples of the gas used for etching include a mixed gas mainly containing a fluorine-based gas such as SF ₆ gas and CF ₄ gas, a mixed gas mainly containing a chlorine-based gas such as Cl ₂ gas and SiCl ₄ gas, and a bromine such as HBr gas. Examples thereof include a mixed gas mainly composed of a system gas. Examples of the dry etching apparatus include a dry etching apparatus using a discharge method such as RIE, magnetron RIE, ECR, ICP, microwave, helicon wave, and NLD.
[0019]
Next, as shown in FIG. 1F, the conductive film 7 and the etching mask resist 8 are removed to obtain the transfer mask 10 of the present invention. Here, only the portion corresponding to the transfer pattern 9 of the conductive film 7 may be etched and penetrated, and the other portion may be left as a part of the antistatic conductive film 11 without being removed.
[0020]
Finally, as shown in FIG. 1G, the antistatic conductive film 11 was formed on the front and back surfaces and side surfaces of the transfer mask 10 by a plasma film forming method, a sputtering method, etc., and the antistatic conductive film was formed. The transfer mask 10a of the present invention is obtained.
As the antistatic conductive film 11, the one used for the conductive film 7 can be used, and the film forming method is also the same.
Although the antistatic conductive film 11 is formed here, this is not essential, and is formed as necessary.
[0021]
【Example】
The present invention will be described in detail with reference to specific examples.
<Example 1>
FIG. 1A to FIG. 1F are explanatory views showing, in partial cross section, an example of a transfer mask manufacturing method according to the present invention. First, as shown in FIG. 1A, an upper single crystal silicon wafer 1 having a plane orientation of (100) and a lower single crystal silicon wafer 2 are bonded together with a silicon oxide film 3 to form an SOI (Silicon on Insulator) substrate 4. Next, a silicon nitride film is formed as a wet etching protective film 5 on both surfaces of the SOI substrate 4 by CVD, and then the wet etching protective film 5 on the lower single crystal silicon wafer 2 side by dry etching using the resist as an etching mask. An opening pattern 6 was formed in the silicon nitride film. (See Fig. 1 (a))
[0022]
Next, using the silicon nitride film of the wet etching protection film 5 as an etching mask, wet etching is performed using a heated potassium hydroxide solution until the lower single crystal silicon wafer 2 reaches the silicon oxide film 3 to form an opening 6a. did. (See Fig. 1 (b))
[0023]
Next, the silicon nitride film of the wet etching protective film 5 was removed by etching with hot phosphoric acid at about 170 ° C., and then the silicon oxide film 3 exposed to the opening 6a was removed by wet etching using a hydrofluoric acid aqueous solution. (See Fig. 1 (c))
[0024]
Next, a Cr film 7 as a conductive film is deposited on the surface facing the opening 6a by sputtering and the bottom surface of the lower single crystal silicon wafer 2a where the opening 6a is formed, and then the transfer mask pattern 9 is deposited. Using the resist 8 patterned as an etching mask, the upper single crystal silicon wafer 1 was dry etched until it reached the Cr film of the conductive film 7 to form a transfer mask pattern 9 on the upper single crystal silicon wafer. (See FIG. 1 (d) and (e))
[0025]
Next, the resist 8 and the Cr film of the conductive film 7 were removed, and the transfer mask pattern 9 was penetrated to obtain a transfer mask 10. (See FIG. 1 (f)). Finally, tantalum was formed as an antistatic conductive film 11 with a thickness of about 1000 angstroms using an electron beam vapor deposition apparatus to obtain a transfer mask 10a for charged beam exposure according to the present invention. (See Fig. 1 (g))
As described above, the transfer mask thus manufactured did not show the notching phenomenon and the deformation of the resist due to the temperature rise of the upper single crystal silicon wafer, and a transfer mask with good pattern accuracy was obtained.
[0026]
【The invention's effect】
As described above, according to the transfer mask manufacturing method of the present invention, in the transfer pattern manufacturing process to the upper single crystal silicon wafer by dry etching of the transfer mask for charged beam exposure, By forming a conductive film instead of a silicon oxide film as an etching stopper, the charge-up of the etching stopper during dry etching is reduced, and the effect of suppressing the occurrence of notching is achieved. In addition, the heat generated in the upper single crystal silicon wafer during dry etching can be easily transferred to the substrate holder of the dry etching device via the conductive film, and the temperature rise of the upper single crystal silicon wafer is suppressed, and the resist is deformed by heat. There is also an effect of suppressing the above. Therefore, a transfer mask having a transfer pattern with excellent dimensional accuracy can be manufactured stably.
In addition, according to the transfer mask of the present invention, there is an effect that the transfer mask pattern of the upper single crystal silicon wafer is high quality without being destroyed by dry etching.
[Brief description of the drawings]
FIGS. 1A to 1F are explanatory views showing, in partial cross section, an example of a method for manufacturing a transfer mask according to the present invention.
FIG. 2 is an explanatory view showing in partial section a notching phenomenon that occurs in a process of dry etching a conventional upper single crystal silicon wafer.
FIG. 3 is a partial cross-sectional view illustrating a conventional process for dry etching an upper single crystal silicon wafer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Upper single crystal silicon wafer 1a ... Upper single crystal silicon wafer 2 with transfer mask pattern formed thereon ... Lower single crystal silicon wafer 2a ... Lower single crystal silicon wafer 3 formed with openings ... Silicon oxide film 3a ... Silicon oxide film 4 with opening formed ... SOI substrate 5 ... Wet etching protective film 6 ... Opening pattern 6a ... Opening 7 ... Conductive film 8... Resist 9 on which transfer mask pattern is formed... Transfer mask pattern 10... Transfer mask 10 a... Transfer mask 11 on which antistatic conductive film is formed. Membrane 20 ... cation

Claims (2)

In a method of manufacturing a transfer mask using an SOI substrate in which two single crystal silicon wafers are bonded with a silicon oxide film, an opening is formed in a lower single crystal silicon wafer to be a support substrate, and then the silicon oxide film is Next, after forming a conductive film on at least the surface of the upper single crystal silicon wafer facing the opening and the bottom surface of the lower single crystal silicon wafer, a transfer mask pattern is formed on the upper single crystal silicon wafer. Then , at least a step of removing the conductive film, and a method for manufacturing a transfer mask, comprising:   2. The conductive film contains at least one of aluminum, titanium, chromium, nickel, copper, zirconium, niobium, molybdenum, palladium, silver, tantalum, tungsten, osmium, platinum, and gold. Manufacturing method of the transfer mask.

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