JP4389440B2 - Transfer mask and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transfer mask used for charged beam exposure such as an electron beam and an ion beam, and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, with the miniaturization and complexity of semiconductor integrated circuits, the formation of fine patterns by charged beam exposure using a charged beam transmission mask has attracted attention. Conventional transfer masks for charged beam exposure are often produced using a member comprising a silicon thin film layer / a silicon oxide layer / a silicon support layer.
[0003]
The manufacturing process is roughly divided into a step of forming an opening reaching the silicon oxide layer by wet etching or dry etching of the silicon support layer using the silicon oxide layer as an etching stopper layer, and dry etching of the silicon thin film layer. And patterning. The exposed silicon oxide layer is finally removed by wet etching.
[0004]
In such a transfer mask manufacturing process, the formation of the opening in the silicon support layer is usually performed by using silicon nitride or the like as an etching mask and dipping in a hot alkaline solution such as a heated potassium hydroxide (KOH) aqueous solution. This is done by etching.
[0005]
In etching of a silicon single crystal with an aqueous potassium hydroxide solution, it is known that the etching rate varies greatly depending on the crystal plane, and the etching proceeds on the (100) plane and the (110) plane, but almost on the (111) plane. Does not progress.
[0006]
Due to such anisotropic etching, when the opening of the silicon support layer having a (100) surface is formed by wet etching with an aqueous potassium hydroxide solution, the side wall of the opening to be formed is flat (111 ) The surface is exposed. Therefore, the surface of the opening side wall of the silicon support layer is flat, but the opening shape is tapered, and there is a problem that the exposed area of the silicon thin film layer forming the transfer pattern is reduced and the transfer mask is enlarged.
[0007]
In order to solve this problem, it is known to use dry etching capable of forming the opening of the silicon support layer vertically or substantially vertically (see, for example, Patent Document 1). By forming an opening having a wall surface perpendicular to the silicon support layer by dry etching, the exposed area of the silicon thin film layer that forms the transfer pattern can be increased, so that an increase in the size of the mask can be suppressed.
[0008]
As dry etching used for forming the opening of the silicon support layer, it is desired that the etching selectivity with the etching mask is high and the side wall perpendicularity is high, and this includes side wall protective plasma etching, low temperature plasma etching, and the like. Is preferred.
[0009]
However, in the formation of the opening of the silicon support layer by dry etching, the thickness of the silicon support layer is usually several hundred μm, so that the etching depth becomes deep and the etching area is several tens of percent of the entire wafer surface. Because of its large size, the amount of silicon etching is extremely large compared to conventional silicon dry etching, and needle-shaped or irregular-shaped dry etching of several μm to several hundred μm is formed on the bottom and side walls of the formed opening. A large amount of residue is formed, the shape of the side wall of the opening is rough, and the unevenness is increased, and a part thereof may be peeled off as a foreign matter of several μm to several hundred μm. Further, there is a problem that these dry etching residue and side wall foreign matter become foreign matter defects of the transfer mask.
[0010]
Although the foreign matter can be removed to some extent by repeatedly performing a silicon cleaning method such as the RCA cleaning method, the peripheral portion of the connection portion between the side wall of the silicon support layer and the silicon thin film layer that forms a vertical or almost vertical angle. It is difficult to remove foreign substances located in the area.
[0011]
A technique of using dry etching and wet etching together to form the opening of the silicon support layer is also known, but the crystal structure of the silicon support layer is limited to a specific plane orientation (see, for example, Patent Document 2). However, there was a problem in practical use, and the contact angle between the silicon support layer and the thin film was as small as 10 to 45 ° (see, for example, Patent Document 3), and the removal of foreign matters was not always sufficient.
[0012]
[Patent Document 1]
JP 2000-331905 A
[Patent Document 2]
Japanese Patent Laid-Open No. 11-150049
[Patent Document 3]
Japanese Patent Laid-Open No. 2000-124117
[Problems to be solved by the invention]
The present invention has been made in view of these problems, and provides a transfer mask having a structure in which foreign matter hardly accumulates at corners (corners) of an opening and has excellent cleaning properties of the accumulated foreign matter, and a method for manufacturing the transfer mask. With the goal.
[0016]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a transfer mask comprising a thin film layer having a predetermined transfer pattern and a silicon support that supports the thin film layer, wherein the silicon support is a surface of the thin film layer. And at least one of the upper end and the lower end of the side wall of the opening has an inclined surface with an angle of 54.74 ± 5.00 degrees with respect to the surface of the thin film layer. A transfer mask is provided.
[0017]
In the transfer mask of the present invention, both the upper end portion and the lower end portion of the side wall of the opening may have an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the thin film layer. Moreover, the pattern which a thin film layer has can be formed in the charged particle scattering layer on a thin film layer.
[0018]
Further, the present invention processes an SOI substrate (Silicon on Insulator) which is a laminate of a silicon thin film layer, a silicon oxide layer, and a silicon support layer, and opens a silicon thin film layer formed in a predetermined transfer pattern. A transfer mask supported by a silicon support layer having a portion, wherein the silicon support layer has an opening sidewall substantially perpendicular to the surface of the silicon thin film layer, and an upper end portion and a lower end portion of the opening sidewall. At least one provides a transfer mask characterized by having an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer.
[0019]
According to the transfer mask of the present invention configured as described above, at least one of the upper end portion and the lower end portion of the opening side wall of the silicon support has an angle of 54.74 ± 5.00 degrees with respect to the surface of the thin film layer. Therefore, it is possible to obtain an excellent structure in which foreign matter is not easily collected at the corner (corner) of the opening, and the collected foreign matter can be easily washed from the corner of the opening. .
[0020]
The above transfer mask of the present invention is produced by the following method.
[0021]
1. Forming an opening that reaches the silicon oxide layer by dry etching in the silicon support layer of the SOI substrate, which is a laminate of a silicon thin film layer, a silicon oxide layer, and a silicon support layer; Forming an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer on at least one of an upper end portion and a lower end portion of the side wall of the opening by performing wet etching. A method for manufacturing a transfer mask, comprising: removing a portion of the silicon oxide layer exposed in the opening, and forming a predetermined transfer pattern on the silicon thin film layer by dry etching.
[0022]
2. Forming an opening that reaches the silicon oxide layer by dry etching in the silicon support layer of the SOI substrate, which is a laminate of a silicon thin film layer, a silicon oxide layer, and a silicon support layer; Forming an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer on at least one of an upper end portion and a lower end portion of the side wall of the opening by performing wet etching. A method for producing a transfer mask, comprising: a step of forming a predetermined transfer pattern on the silicon thin film layer by dry etching; and a step of removing a portion of the silicon oxide layer exposed in the opening.
[0023]
3. Forming a predetermined transfer pattern by dry etching on the silicon thin film layer of the SOI substrate, which is a laminate of a silicon thin film layer, a silicon oxide layer, and a silicon support layer; and forming the silicon oxide layer on the silicon support layer by dry etching Forming an opening reaching the surface of the opening, and performing anisotropic wet etching on the sidewall of the opening, so that at least one of the upper end and the lower end of the opening sidewall is 54 with respect to the surface of the silicon thin film layer. A method of manufacturing a transfer mask, comprising: forming an inclined surface with an angle of .74 ± 5.00 degrees; and removing a portion of the silicon oxide layer exposed in the opening.
[0024]
According to the transfer mask manufacturing method of the present invention described above, since the opening of the silicon support layer is formed by dry etching and subsequent wet etching, the etching residue on the bottom and side walls of the opening of the silicon support layer. Objects are easily removed and the unevenness of the side walls is reduced, so that the generation of foreign matter from the side walls is greatly suppressed.
[0025]
Further, an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer is formed on at least one of the upper end and the lower end of the opening side wall of the silicon support by anisotropic wet etching. For this reason, it is possible to obtain an excellent structure in which foreign matter hardly accumulates at the corner (corner) of the opening, and the accumulated foreign matter can be easily cleaned from the corner of the opening.
[0026]
In the above method for producing a transfer mask, dry etching for forming an opening in the silicon support layer is stopped before reaching the silicon oxide layer, and then anisotropic wet etching is performed to thereby form the opening. While the formation is completed, an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer can be formed on at least one of the upper end portion and the lower end portion of the opening side wall.
[0027]
Further, the step of forming the SOI substrate can be performed by forming the silicon oxide layer on the silicon support layer and bonding the silicon oxide layer and the silicon thin film layer together. By doing so, an SOI substrate in which defects between the silicon support layer and the silicon oxide layer are suppressed can be manufactured.
[0028]
Furthermore, the present invention provides a charged particle beam exposure method comprising a step of irradiating the above-mentioned transfer mask with a charged particle beam and shaping the charged particle beam into a transfer pattern shape.
[0029]
According to the exposure method of the present invention, it is possible to perform pattern exposure with high accuracy on the resist formed on the sample substrate. As a result, it is possible to manufacture a pattern of a semiconductor or the like with a high yield.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a manufacturing process of a transfer mask according to an embodiment of the present invention will be described with reference to FIGS.
[0031]
First, as shown in FIG. 1A, two single crystal silicon wafers 1 and 2 are bonded together via a silicon oxide layer 3, and an SOI substrate 4 comprising a silicon thin film layer / a silicon oxide layer / a silicon support layer is formed. Is made. In such an SOI substrate 4, the thickness of the silicon thin film layer is preferably 0.1 to 20 μm, the thickness of the silicon oxide layer is preferably 0.1 to 2 μm, and the thickness of the silicon support layer is preferably 200 to 1000 μm.
[0032]
The bonding method of the SOI substrate is not particularly limited, but the interface between the silicon support layer and the silicon oxide layer of the SOI substrate is exposed because the silicon oxide layer is exposed to thermal alkali during wet etching after opening the support layer by dry etching. Therefore, it is important to use a method in which a silicon oxide layer is formed on the silicon support layer and the silicon oxide layer formed on the silicon support layer is bonded to the silicon thin film layer. . According to this method, an SOI substrate in which defects at the interface between the silicon support layer and the silicon oxide layer are suppressed can be obtained.
[0033]
Next, as shown in FIG. 1B, a wet etching mask 5 made of silicon nitride, silicon oxide or the like is formed on the entire surface of the SOI substrate 4. These films can be formed by plasma deposition, sputtering, CVD (Chemical Vapor Deposition), thermal oxidation, or the like. Then, a photoresist film is applied to the surface on the silicon support layer side of the SOI substrate 4a covered with the wet etching mask 5, and a photoresist 6 in which the support layer opening pattern 7 is formed is formed by photolithography.
[0034]
Next, as shown in FIG. 1C, the wet etching mask 5 corresponding to the silicon support layer opening exposed from the photoresist 6 is formed by dry etching or wet etching using the photoresist 6 as an etching mask. The wet etching mask 5a in which the support layer opening pattern 7a is formed is formed by removing.
[0035]
Subsequently, as shown in FIG. 1D, the photoresist 6 is used as an etching mask until reaching the silicon oxide layer 3 or reaching the silicon oxide layer 3 by dry etching such as sidewall protection plasma etching or low-temperature plasma etching. The silicon support layer 2 is etched until just before it is formed to form the opening 7b. The pillars 8 and the peripheral support substrate 9 are formed on the silicon support layer 2 by forming the openings 7b.
[0036]
Here, dry etching is used as a method of forming the opening 7b in the silicon support layer 2, but ultrasonic processing, sandblasting, or the like can also be used.
[0037]
The mask for dry etching of the silicon support layer is not particularly limited. A silicon oxide film, a silicon nitride film, a metal film, a metal oxide film, a metal nitride film, or the like can be suitably used instead of the photoresist. When a silicon oxide film or a silicon nitride film is used, dry etching and wet An etching mask common to etching can be obtained.
[0038]
Thereafter, as shown in FIG. 2A, the opening formation of the silicon support layer 2 is completed by wet etching by alkaline liquid immersion such as a heated potassium hydroxide (KOH) aqueous solution, and the opening 7c is obtained. By wet etching, an inclined surface having an angle of 54.74 ± 5.00 degrees is formed at the corner (corner) of the opening 7c.
[0039]
Next, as shown in FIG. 2B, the hydrofluoric acid aqueous solution or the like is removed from the silicon oxide layer 2 exposed in the opening 7c formed in the silicon support layer 2, and then the hot phosphoric acid aqueous solution and hydrofluoric acid aqueous solution are removed. The wet etching mask 5a such as silicon nitride or silicon oxide is removed.
[0040]
Next, as shown in FIG. 2C, a resist such as an electron beam resist or a photoresist is applied to the silicon thin film layer 1 to form a resist 10 in which a fine pattern 11 is formed by electron beam lithography or photolithography.
[0041]
Subsequently, as shown in FIG. 2D, a transfer pattern 11a is formed on the silicon thin film layer 1 by dry etching using the resist 10 as a mask to obtain a transfer mask.
[0042]
The dry etching method and conditions for forming the transfer pattern 11a are not particularly limited. Examples of the dry etching apparatus include dry etching apparatuses using discharge methods such as RIE, magnetron RIE, ECR, ICP, NLD, microwave, helicon wave, and the like. Gases used for etching include mixed gas mainly composed of fluorine-based gas such as CF4 and SF6 gas, mixed gas mainly composed of chlorine-based gas such as Cl2 gas and SiCl4 gas, and mixed mainly composed of bromine-based gas such as HBr gas. Gas etc. are mentioned.
[0043]
In the transfer mask manufacturing process according to the embodiment of the present invention described above, as a method of forming the opening 7c in the silicon support layer 2, first, dry etching or the like is performed, and then wet etching is performed. Stage etching is used. Therefore, etching residues on the bottom and side walls of the opening of the silicon support layer 2 are easily removed. Moreover, the unevenness | corrugation of a side wall is reduced and, therefore, generation | occurrence | production of the foreign material from a side wall can be suppressed. Furthermore, an inclined surface having an angle of 54.74 ± 5.00 degrees can be formed on the upper end portion and the lower end portion of the opening side wall of the silicon support 2 by wet etching. For this reason, it is possible to obtain a structure in which foreign matter hardly accumulates at the corner (corner) of the opening and is excellent in cleaning properties of the accumulated foreign matter.
[0044]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS. In this embodiment, the transfer pattern is formed on the silicon thin film layer after the opening of the silicon support layer is formed. On the contrary, after the transfer pattern is formed on the silicon thin film layer, the opening is formed on the silicon support layer. It may be formed.
[0045]
1 and 2 are cross-sectional views showing an example of a charge beam exposure transfer mask manufacturing process according to an embodiment of the present description. FIG. 3 is an enlarged view of the column after the wet etching is performed after the opening of the silicon support layer is formed by dry etching.
[0046]
First, as shown in FIG. 1A, a silicon oxide layer having a thickness of 1 μm is formed on a single crystal silicon wear (silicon support layer) 2 having a crystal plane orientation of (100) and having a thickness of 500 μm by a thermal oxidation method. 3 was bonded to a 2 μm-thick single crystal silicon wafer (silicon thin film layer) 1 having a crystal plane orientation of (100) to produce an SOI substrate 4. Here, the thicknesses of the silicon support layer 2, the silicon oxide layer 3, and the silicon thin film layer 1 are 500 μm, 1 μm, and 2 μm, respectively, but the thickness of each layer is not particularly limited.
[0047]
Next, as shown in FIG. 1B, a silicon nitride film 5 as a wet etching protective film is formed to a thickness of 0.3 μm on the entire surface of the SOI substrate 4 by the CVD method and covered with the silicon nitride film 5. A SOI substrate 4a was fabricated. Subsequently, a photoresist film was applied to the surface of the SOI substrate 4a on the silicon support layer side, and an opening 7 was formed by photolithography to obtain a photoresist 6.
[0048]
Next, as shown in FIG. 1C, the silicon nitride 5 exposed in the opening 7 is removed by etching using RIE using a mixed gas mainly composed of CF4 gas with the photoresist 6 as an etching mask, Opening 7a was formed.
[0049]
Subsequently, as shown in FIG. 1D, sidewall protective plasma etching by inductively coupled plasma using a mixed gas mainly composed of C3F8 gas, C4F8 gas, Cl2 gas, and SF6 gas using the photoresist 6 as an etching mask, The silicon support layer 2 was etched until it reached the silicon oxide layer 3, thereby forming an opening 7 b in the silicon support layer 2. The pillars 8 and the peripheral support substrate 9 were formed on the silicon support layer 2 by forming the openings 7b.
[0050]
Here, when the dry etching for forming the opening of the silicon support layer 2 is stopped before reaching the silicon oxide layer, the silicon support layer 2 is left with a thickness of several μm to several tens of μm. Stopped.
[0051]
After that, as shown in FIG. 2A, the photoresist 6 is removed by plasma ashing with oxygen gas, and then immersed in a potassium hydroxide solution heated to 85 ° C. to etch the silicon nitride film 5a into an etching mask. As a result, the pillars 8 and the side walls of the peripheral support substrate 9 were etched by 10 μm to form the pillars 8a and the peripheral support substrate 9a.
[0052]
It was confirmed by the scanning electron microscope and the optical microscope that the unevenness of the sidewalls of the support and the peripheral support substrate was significantly reduced by the wet etching.
[0053]
As shown in FIG. 3 in an enlarged manner, the crystal plane 20 was exposed at the ends of the support columns 8a and the peripheral support substrate 9a by wet etching of the side wall, and the crystal plane orientation was (111).
[0054]
Moreover, the angle 23 between the interface 21 between the upper surface of the support 8a and the silicon oxide layer 3 and the interface 22 between the bottom surface of the support 8a and the silicon oxide 5a and the crystal plane 20 is about 54.74 degrees. The cross section was confirmed by observation with a scanning electron microscope.
[0055]
Next, as shown in FIG. 2B, the wafer is immersed in a phosphoric acid aqueous solution heated to 160 ° C. to remove the silicon nitride 5a, and then the support layer opening 7c is wet etched with a hydrofluoric acid aqueous solution. The silicon oxide layer 3 exposed to is removed.
[0056]
Next, as shown in FIG. 2C, an electron beam resist was applied on the silicon thin film layer 1 to form an electron beam resist 10 on which a fine pattern 11 was formed by electron beam exposure.
[0057]
Further, as shown in FIG. 2 (d), a transfer pattern 11a is formed on the silicon thin film layer by RIE using a mixed gas mainly composed of chlorine gas using the electron beam resist 10 on which the fine pattern is formed as an etching mask. Subsequently, the electron beam resist 10 was removed by plasma ashing using oxygen gas to obtain a transfer mask 12 according to this example.
[0058]
In the transfer mask 12 thus produced, no etching residue was present on the bottom and side walls of the opening of the silicon support layer 2. Further, the side wall was smooth, and therefore no foreign matter was generated from the side wall. Further, the angle 23 between the interface 21 between the upper surface of the support 8a and the silicon oxide layer 3 and the interface 22 between the support bottom and the silicon oxide 5a and the crystal plane 20 is about 54.74 degrees, so that the opening portion It was difficult for foreign matter to collect at the corners (corner portions) of this, and the cleaning properties of the collected foreign matter were excellent.
[0059]
【The invention's effect】
As described above, according to the transfer mask of the present invention, since the inclined surface is formed on at least one of the upper end and the lower end of the opening side wall of the silicon support, the corner (corner) of the opening is formed. Thus, it is possible to obtain a structure in which foreign matter is less likely to collect and the cleaning property of the collected foreign matter is excellent.
[0060]
In addition, according to the method for producing a transfer mask of the present invention, the opening of the silicon support layer is formed by dry etching followed by wet etching. The inspection object is easily removed, and the unevenness of the side wall is reduced, so that the generation of foreign matter from the side wall is suppressed.
[0061]
Furthermore, according to the exposure method of the present invention, it is possible to perform pattern exposure with high accuracy for a resist formed on a sample substrate for a long period of time, and as a result, it is possible to manufacture a pattern of a semiconductor or the like with a high yield.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a transfer mask manufacturing process according to an embodiment of the present invention in the order of steps.
FIG. 2 is a cross-sectional view illustrating a transfer mask manufacturing process according to an embodiment of the present invention in the order of steps.
FIG. 3 is a diagram showing a schematic cross-sectional structure of a column after a side wall is etched by wet etching in a transfer mask manufacturing process according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon thin film layer 2 ... Silicon support layer 3 ... Silicon oxide layer 4 ... SOI substrate 4a ... SOI substrate 5 which formed wet etching mask on the whole surface ... Wet etching mask 5a ... Wet etching mask 6 having opening pattern ... Photoresist 7 having opening pattern ... Opening pattern 7a formed in photoresist ... Opening pattern 7b formed in wet etching mask ... Silicon support layer Opening 7c formed on the side wall 8: Side wall wet-etched opening 8 Column 8a: Side wall wet-etched column 9 Peripheral support substrate 9a ... Side wall wet-etched peripheral support substrate 10... Resist with a fine pattern formed 11... Fine pattern 1 formed on a resist a ... transfer pattern 12 formed on the silicon thin film layer ... transfer mask 20 produced according to the present invention ... (111) crystal plane 21 formed on the support by wet etching ... upper surface of the support 8a Interface 22 between the silicon oxide 5a and the bottom surface of the support column 8a and the interface 23 between the silicon nitride 5a and the crystal plane 20, the interface 21, and the interface 22 angle.

Claims (3)

An SOI substrate including a silicon support layer having a (100) surface, a silicon oxide layer formed on the silicon support layer, and a thin film layer bonded to the silicon oxide layer is processed. A transfer mask in which a silicon thin film layer formed in a transfer pattern is supported by a silicon support layer, wherein the silicon support layer has a side wall opening perpendicular to the surface of the silicon thin film layer, and the side wall of the opening The transfer mask is characterized in that a (111) plane is exposed at the upper end portion and the lower end portion of the substrate and has an inclined surface having an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer. Forming a silicon oxide layer on a silicon support layer having a (100) surface and bonding a silicon thin film layer to the silicon oxide layer to form an SOI substrate;
Wherein the silicon support layer of the SOI substrate, forming an opening reaching the silicon oxide layer by dry etching,
By performing anisotropic wet etching on the side wall of the opening, the upper and lower ends of the side wall of the opening are (111) at an angle of 54.74 ± 5.00 degrees with respect to the surface of the silicon thin film layer. ) Forming an inclined surface whose surface is exposed;
Forming a predetermined transfer pattern on the silicon thin film layer , and removing a portion of the silicon oxide layer exposed in the opening ,
The step of forming the opening reaching the silicon oxide layer by dry etching is performed before the step of forming inclined surfaces at the upper end and lower end of the opening sidewall by anisotropic wet etching. A method for producing a transfer mask. A charged particle beam exposure method comprising a step of irradiating the transfer mask according to claim 1 with a charged particle beam and shaping the charged particle beam into a shape of a transfer pattern.

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