JPH0778748A - Aperture mask and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing an aperture mask, which has opening parts for electron beam molding of a superior dimensional accuracy and has a high-electron stopping efficiency. CONSTITUTION:In a method of manufacturing an aperture mask, which is used for an electron beam drawing device of a character projection system, an SiO2 film 23 is formed on one main surface of an Si substrate 21 and thereafter, a Ti film 24 and a Pd film 25 are formed on the film 23 as a conductive film, then, a resist 26 for electron beam is formed as the casting material for a heavy metal thin film. An electron beam of the amount of emission, which is required to expose the resist 26, is emitted in a multitude of times of exposure and the resist is exposed in such a way that the boundaries of the respective beam shots of the beams are not superposed in a drawing in each time, whereby a casting 27 is formed, then, an Au film is grown in the casting 27 by a desired thickness, then, after the casting 27 is removed, the substrate 21 is etched from the side of its rear and openings provided in the film 28 are formed in such a way as to penetrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture mask used in a charged beam drawing apparatus, and more particularly to an aperture mask used in a character projection type charged beam drawing apparatus and a manufacturing method thereof.

[0002]

2. Description of the Related Art An electron beam drawing apparatus which exposes a resist by using an electron beam can obtain an extremely steep beam profile by increasing the electron acceleration voltage to about 50 kV. DRA
It is possible to resolve a line width of 0.15 μm or less, which is necessary for drawing M. However, the weak point of such a high-resolution electron beam drawing apparatus is low throughput.

In recent years, a character projection (CP) system as shown in FIG. 9 has been proposed as a system for dramatically improving this throughput. A rectangular aperture A is formed in the first shaping aperture mask 1, and a character pattern (aperture) C1, C2, C repeatedly appearing in a memory LSI or the like is formed in the second shaping aperture mask 2 together with an aperture B for variable shaping.
3 and C4 are formed.

When a repetitive pattern is drawn, the beam 4 formed through the aperture A of the mask 1 is selectively irradiated onto the character pattern C of the mask 2 so that the beam pattern 5 generated by passing through the mask 2 is formed. The reduced projection is performed on the sample 3. In this case, a pattern that requires a large number of shots in the conventional variable shaping drawing method or the like can be exposed by one irradiation, so that the drawing speed can be greatly improved.

When the CP method is actually applied to LSI drawing, it is necessary to manufacture an aperture mask (stencil mask) having a complicated opening shape with high accuracy. In the drawing of DRAM of 1 Gbit or more, which requires a minimum line width of 0.15 μm, the drawing accuracy for the line width is ± 0.0
1 μm or less is required. If the reduction ratio of the optical system of the drawing apparatus is 1/40, the processing accuracy of the aperture opening portion must be less than ± 0.4 μm.

[0006] In the conventional fabrication of the CP aperture, a silicon (Si) semiconductor manufacturing technique suitable for fine processing has been used. That is, the main material of the aperture mask is S
A thin film of i single crystal is used for RIE (Reactive Ion Etch
ing: reactive ion etching) was used to form the opening.

By the way, the thickness of the aperture mask is determined under the condition that the electron beam can be completely blocked. For example, in order to completely block 50 keV electrons with a Si thin film, a film thickness of about 20 μm is required. However, 20μ
When trying to form a deep opening of m by RIE,
It is difficult to make the side wall of the opening completely vertical, and it may be slanted (tapered) or arced.

When the side wall of the opening of the aperture mask is not completely vertical as described above, the shape accuracy of the formed electronic image is deteriorated. In particular, regarding the inclination, as the film thickness of the mask increases, even a slight inclination greatly affects the shape accuracy of the electronic image. As in the above-mentioned example, in order to make the shape accuracy of the electron image ± 0.01 μm or less, that is, the processing accuracy of the sidewall of the opening is less than ± 0.4 μm
In the case of a Si thin film with a thickness of 20 μm, the inclination of the side wall of the opening must be 1 deg. Or less with respect to the normal direction. However, such processing is practically impossible with the current technology.

On the other hand, when a heavy metal such as gold (Au) or tungsten (W) is used for the material of the aperture mask, the film can be made thinner than when Si is used. For example, the film thickness required to completely block 50 keV electrons is 3.8 μm for Au and W compared with 20 μm for Si.
Good. When the film thickness is thin, deterioration of accuracy due to the inclination of the side wall of the opening is suppressed as compared with the case where the film thickness is thick. In fact, when the film thickness is 3.8 μm, in order to reduce the processing accuracy of the side wall of the opening to ± 0.4 μm or less, the inclination of the side wall may be set to 6 deg.

By the way, there is a method of forming an Au film by using a resist as a template and a plating method in order to accurately form the opening portion of the aperture mask. This method is
This method has a proven track record in the production of masks for line exposure, and has a great advantage in terms of process simplification.
When an electron beam resist (for example, PMMA) is used as the mold, the mold is less deformed during plating and the plating solution does not soak into the bottom of the mold, so that an Au thin film having a vertical edge profile can be formed. it can.

However, in the X-ray exposure mask, Au is used.
The film thickness is about 0.5 μm, while 50 ke
The CP aperture mask for V electron beam requires a film thickness of about 4 μm as described above. To use it as a template for an Au film having a thickness of 4 μm, the resist needs to have a thickness of about 5 μm. However, in the electron beam resist, as the film becomes thicker, resist heating occurs during writing and the pattern accuracy deteriorates. Also, the resist profile after development becomes arcuate or skirting does not cause verticality. Further, if the precision of the shot connection of the variable shaped beam and the connection of the drawing field is not sufficient, there arises a problem that the roughness of the pattern edge is increased.

[0012]

As described above, the conventional CP
In the aperture mask of the method, it is extremely difficult to form a beam forming opening with good dimensional accuracy, and there is a problem that the beam connecting accuracy and the drawing field connecting accuracy become insufficient and the drawing accuracy decreases. .

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an aperture mask having a high electron blocking efficiency, which has an opening for forming a charged particle beam with excellent dimensional accuracy, and its manufacture. To provide a method.

[0014]

In order to solve the above problems, the present invention employs the following configurations. That is, the present invention is used in a character projection type charged beam drawing apparatus, in which a plurality of types of openings having desired pattern shapes are formed, and a beam of any pattern shape is selectively irradiated with a charged particle beam. In the aperture mask to be shaped, a heavy metal thin film is used as a beam blocking and blocking film used for shaping the charged particle beam.

The preferred embodiments of the present invention are as follows. (1) The heavy metal film used for the beam blocking film must be gold or tungsten. (2) For a Si substrate with many aperture masks,
A cutting groove for cutting out the aperture mask is provided in advance. (3) A beam blocking film used for shaping the charged particle beam, a peripheral thin film made of the same material and surrounding the blocking film, and a bridge connecting the blocking film and the peripheral thin film. Be equipped. (4) The surface orientation of the Si substrate used for the aperture mask is (110).

According to the present invention, in the above-described method for manufacturing an aperture mask, a buffer film is formed on one main surface of a silicon substrate, and then a conductive film is formed on the buffer film.
Next, a mold for selectively growing the heavy metal thin film is formed on the conductive film, then the heavy metal thin film is grown to a desired thickness in the mold, and after removing the mold, the back surface side of the heavy metal thin film is removed. This is a method in which the opening provided in the thin film is removed so as to penetrate it.

The preferred embodiments of the present invention are as follows. (1) In the mold fabrication process, an electron beam resist was used as the template material for the heavy metal thin film, a charged particle beam was used to draw the resist, and the irradiation dose required to expose the resist was divided into multiple exposures. And the beams are irradiated so that the boundaries of the beam shots do not overlap each other in each writing. (2) As a step of growing the heavy metal thin film, the heavy metal thin film was grown by a plating method. (3) Polycrystalline Si film is used as the conductive film, Si oxide is used as the template material of the heavy metal thin film, and the Si oxide is polycrystalline Si using the etching gas containing CF ₃ + CO + Ar with the resist or carbon film as a mask. Processing was performed until the film was exposed to form a template, and damage to the surface of the polycrystalline Si film caused in the etching process was removed in a cleaning process including at least choline treatment. (4) As the step of growing the heavy metal thin film, the heavy metal thin film was grown by the selective CVD method of tungsten. (5) In the step of growing the heavy metal thin film in which the heavy metal thin film is grown by the selective CVD method of tungsten, the growth of the tungsten film is performed in multiple stages, and the film annealing step is provided every time.

[0018]

According to the present invention, by using a heavy metal thin film for the beam blocking film, the film thickness can be made sufficiently thinner than Si, and the precision of the opening can be improved. That is, it is possible to provide an aperture mask having a high electron blocking efficiency, which facilitates the aperture mask manufacturing process and has an opening for forming a charged particle beam with excellent dimensional accuracy.

Further, by providing a bridge connecting the beam blocking film and the peripheral thin film made of the same material and surrounding the film, the heat generated in the beam blocking film can be efficiently released. The temperature rise of the beam blocking film can be suppressed. Also, as a process of manufacturing a mold using an electron beam resist, the irradiation amount required for exposing the resist is divided into a number of times of exposure, and irradiation is performed.
In addition, by irradiating the beams so that the boundaries of the beam shots do not overlap each other in each writing, the influence of resist heating can be suppressed.

[0020]

The details of the present invention will be described below with reference to the illustrated embodiments. (First Embodiment) FIG. 1 is for explaining the structure of an aperture mask according to the first embodiment of the present invention.
Is a cross-sectional view and (b) is a perspective view. In the aperture mask 10 of this embodiment, together with the arrow-shaped aperture B for generating the variable shaped beam, a repetitive pattern is drawn.
A plurality of character apertures C1, C2, C3, C4 for so-called character projection drawing are arranged.

The aperture mask 10 comprises a thin film portion 8 and a substrate portion 1 supporting the thin film portion 8. The substrate portion 1 is made of silicon single crystal and has a thickness of about 600 μm. The thin film portion 8 is composed of a plurality of layers 2, 3, and 4 including, for example, a gold (Au) layer 5, and the gold layer 5 has a thickness sufficient to block an electron beam, for example, 4 μm. The electron beam 7 with which the aperture mask 10 is irradiated is shaped into a shape defined by the opening portion of the thin film portion 8 and is reduced and projected onto a sample surface (not shown).

FIG. 2 is a sectional view showing the manufacturing process of the aperture mask according to this embodiment. First, as shown in FIG. 2A, a silicon oxide film (SiO 2) is formed on the main surface of a Si crystal substrate 21 having a plane orientation (100) by using a thermal oxidation furnace.
₂ ) Form 23 with a thickness of 1.5 μm. Furthermore, a silicon nitride film (SiN) is formed on the back surface of the substrate by using a low pressure CVD apparatus.
22 is formed to a thickness of 150 nm. Then, a Ti film (100 nm) 24 and a Pd film (50 nm) 25 as a conductive film are sequentially formed on the main surface of the substrate as a base of Au plating by using a sputtering film forming apparatus.

Next, as shown in FIG. 2B, an electron beam resist (PMMA) 26 of 5 μm is formed on the plating base.
It is applied to a thickness of m using a spin coater. At this time,
For example, PMMA having a viscosity of 65 cP is spin-coated at 300 rpm and baked at 180 ° C. for 60 minutes in an oven to obtain a thickness of 1 μm. By repeating this step 5 times, a film thickness of about 5 μm can be obtained.

Next, an aperture pattern is drawn by using an electron beam direct drawing apparatus (acceleration voltage 40 kV in this embodiment). When the resist is thick as in this embodiment,
To obtain a vertical resist profile, the dose can be increased above normal and the development time can be shortened accordingly. In this example, 300 to 500 μC / cm ^2, which is 3 to 5 times the normal dose, was applied.

However, if this amount of irradiation is applied once, resist heating will occur and the resist will melt, worsening the edge roughness of the pattern, and in the remarkable case, boiling resist will scatter and stain the drawing chamber. There is a fear. Therefore, with a dose of 25 μC / cm ² that can suppress the influence of resist heating once, a drawing of 12 to 20 layers was performed.

At this time, if the beam shots of the same shape are drawn in the same drawing field, the error between the beam shots and the connection between the drawing fields becomes more remarkable due to the multiple writing, and the edge roughness of the drawing pattern is deteriorated. Let Therefore, the size of the drawing field and the size and position of the shot are changed for each drawing to change the position of the joint for each drawing, thereby averaging the edge roughness of the pattern. After drawing, use isopentyl acetate for 1 minute depending on the dose.
Develop for 3 minutes and rinse with isopropyl alcohol to form template 27.

Then, as shown in FIG. 2C, the Au thin film 28 is electroplated to form the conductive film 25 inside the mold 27.
A film is formed on top. At this time, the dense film 28 having a high density can be formed by using the pulse plating method.

Next, as shown in FIG. 2 (d), when the resist 26 is removed by an oxygen plasma ashing apparatus, an opening portion of an aperture pattern is formed in the Au thin film 28. Next, after applying a photoresist 29 to the back surface of the substrate 21 and performing pre-baking, a double-sided exposure apparatus is used to align the position with the aperture pattern of Au on the main surface, and a pattern 30 for opening the substrate is formed on the back surface of the wafer. To form. afterwards,
RIE apparatus using the photoresist 29 as a mask on the SiN film 22 on the back surface of the substrate (etching gas is CF ₄ : O ₂ ).
Etching using.

Then, as shown in FIG. 2 (e), SiN
Using the film 22 as a mask, anisotropic wet etching of the Si (100) substrate 21 is performed with an aqueous potassium hydroxide (KOH) solution to form a tapered opening portion in which the (111) plane 31 is exposed on the back surface of the substrate. . When the concentration of the KOH aqueous solution is 30% by weight and the temperature is 90 ° C., the (100) plane of silicon can be etched at a rate of 2.2 μm / min. At this time, the upper surface of the substrate is protected by a jig (not shown) in which a plate made of a fluororesin and an O-ring made of a fluororubber are combined so that the etching solution does not get around. In addition, the SiO ₂ film 23 under the plating base
Is used as a stop layer for KOH etching.
When the KOH etching reaches this stop layer, the etching is finished.

After that, the plating bases 24 and 25 at the opening portion of the aperture pattern are removed with a mixed solution of sulfuric acid and hydrogen peroxide, and further SiO ₂ is added with an ammonium fluoride solution.
The SiN film 22 is removed from the film 23 with hot phosphoric acid.

As described above, according to the present embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask fabrication process is facilitated and the charged particle beam forming opening portion with excellent dimensional accuracy is obtained. It is possible to realize an aperture mask with high electron blocking efficiency. In particular, when exposing a resist, the irradiation amount of one time is reduced and the irradiation amount of three times the normal irradiation amount is increased by irradiation of a large number of times.
Since the irradiation amount is 5 times, a vertical profile can be obtained even with a thick resist, and a good template having a vertical sectional shape can be formed. (Second Embodiment) As described in the first embodiment, when the aperture mask is manufactured, KOH anisotropic etching is performed from the back surface of the Si substrate having the plane orientation (100) to (1
11) When forming a tapered opening reaching the main surface of the substrate with the surface as the side wall, the length of one side of the square of the bottom surface of the back surface opening is 2 ^1/2 × (thickness of substrate) + (opening The length of one side of the upper surface). When it is attempted to form the openings individually for each aperture as in the first embodiment, the aperture intervals must be widened in accordance with the size of the opening on the back surface.
For example, when the thickness of the substrate is 600 μm and the length of one side of the aperture opening region (the illuminated portion), that is, the length of one side of the upper surface of the opening is 100 μm, one side of the bottom surface of the opening is 950 μm. 850 spacing between apertures
Must be at least μm.

By the way, in the electron beam drawing apparatus, the aperture arranged on the aperture mask is selected by the aperture selection deflector provided upstream of the beam. Therefore, the area where the aperture can be arranged is this deflector. Limited to the deflectable area. Therefore, the number of apertures that can be arranged on the aperture mask is limited.

Here, assuming that the deflectable area of the aperture selection deflector is 2 mm □, as can be seen from the above example, only a maximum of 2 × 2 = 4 types of apertures are arranged on a 600 μm thick substrate. It will not be possible. In order to arrange a larger number of apertures, the thickness of the substrate must be reduced. In the above example, the substrate thickness is 180 μm
Then, a maximum of 6 × 6 = 36 kinds of apertures can be arranged.

On the other hand, when a substrate of Si single crystal having a plane orientation (110) is used, the number of apertures that can be arranged can be made independent of the thickness of the substrate as described below.
Moreover, the number of apertures can be increased more than in the case of the above (100) substrate.

A Si substrate having a plane orientation (110) has (11
There is a (111) plane in which the 0) plane (both sides of the substrate) is vertically cut and the (100) plane is cut by θ = tan ⁻¹ (2 ^1/2 ).
Therefore, by KOH anisotropic etching, (110)
It is possible to form a groove-shaped opening having a side wall of (111) plane perpendicular to both surfaces of the Si substrate. The aperture may be arranged along the groove-shaped opening.

FIG. 3 is a cross-sectional view showing the manufacturing process of the aperture mask according to the second embodiment of the present invention. First,
As shown in FIG. 3A, a Si crystal substrate 41 having a plane orientation (110) is used, and a silicon oxide film 23 and a silicon nitride film are formed on the main surface and the back surface of the substrate 41 in the same manner as in the first embodiment. A film 22 is formed, and then a Ti film 24 and a Pd film 25 are formed as a base for Au plating.

Then, as shown in FIGS. 3B to 3D, electron beam resist PM is obtained in the same manner as in the first embodiment.
The MA 27 is applied, the exposure is divided into a plurality of times, and the development is further performed to form the template 27. Then, A
A u thin film 28 is formed by electrolytic plating, and the resist 26 is removed by an oxygen plasma ashing device. Then the substrate 41
After the photoresist 29 is applied to the back surface of the substrate and pre-baked, a double-sided exposure device is used to align the position with the Au aperture pattern on the main surface to form a substrate opening pattern 30 on the wafer back surface. Next, S on the back side of the substrate
RIE using the iN film 22 with the photoresist 29 as a mask
Etching is performed using a device (etching gas is CF ₄ : O ₂ ).

Then, as shown in FIG. 3 (e), SiN
Using the film 22 as a mask, anisotropic wet etching of the Si (110) substrate 41 is performed with an aqueous potassium hydroxide (KOH) solution to form an opening portion having a vertical cross-sectional shape in which the (111) plane 32 is exposed on the back surface of the substrate. To do. Where KO
When the concentration of the H 2 aqueous solution is 30% by weight and the temperature is 90 ° C., the (100) plane of silicon can be etched at a rate of 2.2 μm / min. At this time, the upper surface of the substrate is protected so that the etching solution does not come around. Further, the SiO ₂ film 23 under the plating base is used as a stop layer for KOH etching. When the KOH etching reaches this stop layer, the etching is finished.

After that, as in the first embodiment, the plating bases 24 and 25 at the openings of the aperture pattern are removed with a mixed solution of sulfuric acid and hydrogen peroxide, and the SiO ₂ film 23 is further removed with an ammonium fluoride solution. SiN with hot phosphoric acid
The film 22 is removed.

As described above, according to the present embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask forming process for facilitating the aperture mask manufacturing process and excellent dimensional accuracy is facilitated. It is possible to realize an aperture plate having a high electron blocking efficiency. Furthermore, by using a Si single crystal substrate having a plane orientation (110), the number of apertures that can be arranged can be made independent of the thickness of the substrate.
0) The number can be increased as compared with the case of the substrate. (Third Embodiment) FIG. 4 is a sectional view showing a manufacturing process of an aperture mask according to a third embodiment of the present invention. In this embodiment, a selective CVD method of tungsten is used as a method of forming the beam blocking film.

First, as shown in FIG. 4A, a thermal SiO ₂ film 52 having a thickness of 1.5 μm is formed on the main surface of a Si substrate 51 having a plane orientation (100). Then, on the back of the substrate,
A SiN film 53 is formed to a thickness of 150 nm using a low pressure CVD apparatus. Furthermore, on the thermal SiO ₂ film 52 on the main surface of the substrate,
The polycrystalline Si film 54 is 1.0 μm thick by using an LPCVD device.
The thickness of the BPSG film 55 is 4.0 μm using a normal pressure CVD apparatus.
Sequentially formed with a thickness of m. A CVD-SiO ₂ film may be used instead of the BPSG film 55. Then, the substrate 51 is annealed at 800 ° C. for 30 minutes.

Then, as shown in FIG. 4B, BPS
After coating the resist 56 on the G film 55, using a light reduction projection exposure apparatus or an electron beam direct drawing apparatus,
Expose the aperture pattern. After developing the resist 56, the resist 56 is subjected to a surface hardening treatment using ultraviolet rays.

Next, using the resist 56 as a mask, R
The BPSG film 55 is etched using the IE device. At this time, the etching gas is, for example, CHF ₃ + CO + A
When set to r, the opening (mold) 5 with a side wall close to vertical 5
7 can be formed. Then, after removing the resist 56, a damaged layer (not shown) formed on the surface of the polycrystalline Si film 54 under the BPSG film 55 in the above RIE process is removed by choline treatment. By this treatment, the adhesion between the CVD-tungsten film 58 described below and the underlying polycrystalline Si film 54 is improved.

Next, as shown in FIG. 4C, a W film 58 is selectively formed on the polycrystalline Si film 54 by the selective CVD method of tungsten. The film forming conditions at this time are, for example, a substrate temperature of 340 ° C., tungsten hexafluoride (WF ₆ ) and silane (SiH ₄ ) of 20 scc each.
m, 8 sccm, film forming pressure is 4.5 mTorr. The film forming rate under this condition is about 100 nm / min. At this time, for example, W film formation is divided into three times with a thickness of 1.3 μm, and vacuum annealing is performed at 500 ° C. for each time. Such a multi-stage film forming process is effective for forming a film having a thickness of 3 μm or more without peeling.

Then, as shown in FIG. 4D, the BPSG film 55 in the portion corresponding to the aperture opening is wet-etched with an ammonium fluoride solution, and the polycrystalline Si film 54 is removed by RIE. Subsequently, a photoresist 59 is applied on the SiN film 53 on the back surface of the substrate, and a double-sided exposure device is used to align the position with the aperture pattern on the front side to form a pattern for opening the substrate on the back surface of the wafer. After that, the substrate opening pattern 60 is formed on the SiN film 53 by using RIE.

Then, as shown in FIG. 4 (e), SiN
Using the film 53 as a mask, anisotropic wet etching of the Si (100) substrate 51 is performed by KOH anisotropic etching to form a tapered opening 62 in which the (111) plane 61 is exposed on the back surface of the substrate. Here, when the concentration of the KOH aqueous solution is 30% by weight and the temperature is 90 ° C., the (100) plane of silicon can be etched at a rate of 2.2 μm / min. At this time, as in the first embodiment, the upper surface of the substrate is protected so that the etching solution does not come around. The SiO ₂ film 52 under the W film 58 is
It is used as a KOH etching stop layer, and etching is terminated when the KOH etching reaches this stop layer.

After that, as in the first embodiment, the W film bases 52 and 54 at the opening portion of the aperture pattern are removed with an ammonium fluoride solution, and the SiN film 3 is heated with hot phosphoric acid.
Remove 2.

As described above, according to this embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask manufacturing process is facilitated and the charged particle beam forming opening portion with excellent dimensional accuracy is obtained. It is possible to realize an aperture plate having a high electron blocking efficiency. (Fourth Embodiment) In the second embodiment, the (110) Si substrate is used to increase the numerical aperture to be arranged on the aperture mask, but here, another example for increasing other numerical apertures will be described. This will be described with reference to FIGS. 5 and 6.

First, as shown in FIG. 5A, a silicon oxide film 22 having a thickness of 1.5 μm is formed on both surfaces of a Si crystal substrate 21 having a plane orientation (100), and is formed on one main surface. Au
As a plating base, a Ti film (100 nmA) 24 and a Pd film (50 nm) 25 are sequentially formed.

Then, as shown in FIG. 5B, similarly to the first embodiment, an electron beam resist PMMA 26 is formed by coating on the plating base, and an aperture pattern is drawn. After drawing, it is developed using isopentyl acetate for 1 to 3 minutes depending on the irradiation amount, and rinsed with isopropyl alcohol to form the template 27. Then, as shown in FIG. 5C, the Au thin film 28 is formed on the conductive film 25 inside the mold 27 by electrolytic plating in the same manner as in the first embodiment. At this time, an opening portion of the aperture pattern is formed.

Then, as shown in FIG.
1 is thinned, the back surface of the substrate 21 is lapped.
The thickness of the substrate 21 after lapping is determined by the numerical aperture arranged on the aperture mask.

Next, as shown in FIG. 6A, the substrate 2
As a mask material for KOH etching on the back surface of 1.
A carbon film (C) 63 is formed. At this time, the sputtered C film 63 or the sputtered C film 63 continuously formed on the sputtered silicon (Si) film is used. The reason for this is that since the metal (Au) is already present on the main surface, the process in which the substrate temperature rises to 700 to 800 ° C.
This is because, for example, LPCVD of SiN cannot be used.

Sufficient KO is required for the sputter / C film 63 itself.
Although it has H-etching resistance, the C film 63 may peel off during etching if the state of the substrate surface at the time of sputtering, for example, if the contamination is severe. Sputtering / C film 63 KOH
Since the adhesiveness at the time of etching depends on such contamination of the substrate surface, it is necessary to take the following measures in the manufacturing process up to that point. For example, just before sputtering
After polishing the surface of the substrate 21, it is effective to immerse the substrate 21 in a dilute hydrofluoric acid solution or to apply a protective film such as SiO ₂ just before sputtering.

As another method, there is a method in which a film having good adhesion to the Si substrate, for example, Si is first formed and then C is continuously formed thereon. Since Si immediately after sputtering is clean, the adhesion of the C film increases. Since the sputter / C film 63 is a conductive film, it has an advantage that it need not be finally peeled off. Further, the film stress is smaller than that of the SiN film. After forming a sputter / Si film with a thickness of 100 nm on the back surface of the substrate, a sputter / C film 63 is continuously formed (without exposing to the atmosphere) with a thickness of 150 nm.

Next, as shown in FIG. 6B, the resist 26 is removed. Then, after applying a photoresist 29 to the back surface of the substrate 21 and performing pre-baking, a double-sided exposure apparatus is used to align the position with the Au aperture pattern on the main surface to form the substrate opening pattern 3 on the back surface of the wafer.
Form 0. After that, the C film 63 on the rear surface of the substrate is etched using the RIE device (etching gas is CF ₄ : O ₂ ) using the photoresist 29 as a mask.

Then, as shown in FIG. 6C, this C
Using the film 63 as a mask, anisotropic wet etching of the Si (100) substrate 21 is performed with an aqueous potassium hydroxide (KOH) solution to form a tapered opening portion in which the (111) plane 31 is exposed on the back surface of the substrate. . When the concentration of the KOH aqueous solution is 30% by weight and the temperature is 90 ° C., the (100) plane of silicon can be etched at a rate of 2.2 μm / min. At this time, as in the first embodiment, the upper surface of the substrate is protected so that the etching solution does not come around. The SiO ₂ film 23 under the plating base is K
It is used as a stop layer for OH etching, and when it reaches the stop layer, KOH etching ends.

After that, as in the first embodiment, the plating bases 24 and 25 at the openings of the aperture pattern are removed with a mixed solution of sulfuric acid and hydrogen peroxide, and the SiO ₂ film 23 is further removed with an ammonium fluoride solution. Remove.

As described above, according to the present embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask forming process for facilitating the manufacturing process of the aperture mask and having an excellent dimensional accuracy is achieved. It is possible to realize an aperture mask having a high electron blocking efficiency having a portion. Also, since the substrate is thinly cut by lapping, the number of apertures provided in the aperture mask can be increased. Further, by forming the carbon film after the above-mentioned substrate lapping, there is an advantage that the KOH solution resistant film after thinly grinding the Si substrate can be easily obtained. (Fifth Embodiment) FIG. 7 is a sectional view showing a manufacturing process of an aperture mask according to a fifth embodiment of the present invention. In this embodiment, a large amount of aperture masks collectively made on a Si substrate can be easily cut into individual pieces without being destroyed.

The steps up to the steps shown in FIGS. 7A to 7C are the same as the steps shown in FIGS. 2A to 2C, and after this step, as shown in FIG. After applying a photoresist 29 to the back surface of the substrate 21 and performing pre-baking, a substrate opening pattern 40 is formed on the back surface of the wafer by aligning the position with the Au aperture pattern on the main surface using a double-sided exposure device. To do. At this time, the line pattern 70 for dicing is formed in accordance with the size of the aperture mask mounted on the electron beam drawing apparatus. At this time, if the direction of the dicing line 70 is made to coincide with the cleavage direction of the Si crystal, dicing becomes easier.

When the substrate has a thickness of D, it is preferable to pattern a line having a thickness of less than 2 ^1/2 · D on the etching mask. Then, the SiN film 2 on the back surface of the substrate
2 is etched using the RIE device (etching gas is CF ₄ : O ₂ ) using the photoresist 29 as a mask.

Then, as shown in FIG. 7 (e), SiN
Using the film 22 as a mask, anisotropic wet etching of the Si (110) substrate 21 is performed with an aqueous solution of potassium hydroxide (KOH) to form a tapered opening portion in which the (111) surface 31 is exposed on the back surface of the substrate and for dicing. V groove 71 is formed. The concentration of the KOH aqueous solution is 30% by weight, and the temperature is 9
When the temperature is 0 ° C, the (100) plane of silicon is 2.2μ.
It can be etched at a rate of m / min.

At this time, as in the first embodiment, the upper surface of the substrate is protected so that the etching solution does not come around.
Further, the SiO ₂ film 33 under the plating base is used as a stop layer for KOH etching, and when the stop layer is reached, KOH etching is completed. At this time, the V-grooves 71 for dicing remain unchanged after being etched to a certain shape by the SiN film 22.

After that, as in the first embodiment, the plating bases 24 and 25 at the openings of the aperture pattern are removed with a mixed solution of sulfuric acid and hydrogen peroxide, and the SiO ₂ film 23 is further added with an ammonium fluoride solution. With hot phosphoric acid
The iN film 22 is removed.

As described above, according to the present embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask fabrication process is facilitated and the charged particle beam forming opening portion with excellent dimensional accuracy is obtained. It is possible to realize an aperture mask with high electron blocking efficiency. Furthermore, since the V-groove for cutting is provided in advance for each aperture mask of the Si substrate, it is not necessary to write a cutting line using a diamond pen or the like, and the aperture mask can be cut out very easily. (Sixth Embodiment) In the aperture mask 10 as shown in FIG. 1, the electron beam absorbed in the thin film portion 8 is converted into heat and raises the temperature. This temperature rise induces mechanical deformation of the aperture mask 10 and deteriorates the geometry of the beam that is reduced and projected on the sample surface. Therefore, heat generation caused by absorption of the electron beam should be suppressed as much as possible. For this purpose, heat is efficiently absorbed from the thin film portion 8 of the aperture mask 10,
It is necessary to suppress the temperature rise of the aperture mask itself as much as possible.

FIG. 8 is a perspective view showing the structure of an aperture mask according to the sixth embodiment of the present invention which solves the above-mentioned problems. The same parts as those of the aperture mask shown in FIG. 1 are designated by the same reference numerals, and different parts will be described in detail.

On the aperture mask 80, the character
A projection opening C and a molding deflection opening B are provided. All of these openings are formed in the center of the first heavy metal thin film 5 having an area slightly larger than the electron beam with which they are irradiated. This ensures that the electron beam is blocked and is kept as small as possible in order to minimize the thermal deformation of the thin film portion caused by the temperature rise due to the electron beam irradiation.

A second heavy metal thin film 81 is provided around the heavy metal thin film 5 so as to surround it. The thin film 81 is connected to an external heat absorber (not shown). A bridge 82 is made of the same metal between the first heavy metal thin film 5 and the second heavy metal thin film 81. As a result, the heat generated in the heavy metal thin film 5 can be efficiently transferred to the heavy metal thin film 81 via the bridge 82, and the temperature rise in the heavy metal thin film 5 for blocking beam blocking can be suppressed.

The method of manufacturing the aperture mask according to this embodiment will be described below with reference to FIG. First, as shown in FIG. 2A, as in the first embodiment, a silicon oxide film 23 is formed to a thickness of 1.5 μm on the main surface of a Si crystal substrate 21 having a plane orientation (110). A silicon nitride film 22 is formed to a thickness of 150 nm on the back surface of the substrate. Further, a Ti film (100 nm) 24 and a Pd film (50 nm) 25 are sequentially formed as a base for Au plating. Then, an electron beam resist PMMA 26 having a thickness of 5 μm is applied onto the plating base using a spin coater.

Then, the electron beam direct writing apparatus (acceleration voltage 40 kV in this embodiment) is used to write the aperture pattern and the pattern of the second heavy metal thin film 81 and the bridge 82 so as to surround the aperture pattern. In the case where the resist is thick as in this embodiment, in order to obtain a vertical resist profile, the irradiation dose may be increased more than usual and the development time may be shortened accordingly. In the present embodiment, as in the first embodiment, the dose of 25 μC / cm ² which can suppress the influence of resist heating is set to 12 times or more.
Drawing was performed 20 times, and 300 to 500 μC / cm ^2, which is 3 to 5 times the normal irradiation amount, was irradiated. After drawing, it is developed using isopentyl acetate for 1 to 3 minutes depending on the irradiation amount, and rinsed with isopropyl alcohol to form the template 27.

Thereafter, as shown in FIGS. 2 (c) to 2 (e), the Au thin film 28 is formed on the conductive film 25 inside the mold 27 in the same manner as in the first embodiment, and then the resist is formed. 26
Is removed, and an opening portion of the aperture pattern is formed in the Au thin film 28. In addition, photoresist 2 on the back side of the substrate
9 is applied and a pattern 30 for opening a substrate is formed on the back surface of the wafer.
The N film 22 is selectively etched. Then, the SiN film 22
Is used as a mask to perform anisotropic wet etching of the Si (110) substrate 21 to form a tapered opening portion in which the (111) plane 31 is exposed on the back surface of the substrate. After that, the plating bases 24 and 25 at the openings of the aperture pattern are removed with a mixed solution of sulfuric acid and hydrogen peroxide, and further, the SiO ₂ film 23 is removed with an ammonium fluoride solution and the SiN film 22 is removed with hot phosphoric acid. As a result, the structure shown in FIG. 8 is completed.

As described above, according to this embodiment, by using the heavy metal thin film as the thin film for blocking the electron beam, the aperture mask fabrication process is facilitated and the charged particle beam forming opening portion with excellent dimensional accuracy is obtained. It is possible to realize an aperture mask with high electron blocking efficiency. In addition to this, the following effects are obtained in this embodiment.

A heavy metal thin film 81 is provided around the heavy metal thin film 5 of the character projection opening C on the aperture mask and the shaping deflection opening B so as to surround the same. This thin film 81 is an external heat absorber (not shown).
Since the bridge 82 is made of the same metal between the thin film 5 and the thin film 81, the heat generated in the thin film 5 is efficiently transferred to the thin film 81 through the bridge 82. The temperature rise can be suppressed. As a result, mechanical deformation of the aperture mask due to temperature rise can be suppressed, and deterioration of the geometrical dimension of the beam reduced and projected on the sample surface can be minimized.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be carried out without departing from the scope of the invention. Although the embodiment has been described as an aperture mask for an electron beam writing apparatus, the present invention is not limited to this and the present invention can be similarly applied to an aperture mask for an ion beam writing apparatus. Further, the conditions such as the material and film thickness of the heavy metal thin film can be appropriately changed according to the specifications.

[0074]

As described above in detail, according to the present invention, by using a heavy metal thin film as a thin film for blocking a charged particle beam, the manufacturing process of the aperture mask is facilitated and the charged particles with excellent dimensional accuracy are provided. It is possible to realize an aperture mask with a high electron blocking efficiency having a beam forming opening portion. As a result, by using this, it is possible to provide a charged beam drawing apparatus that can obtain a highly accurate beam image.

[Brief description of drawings]

FIG. 1 is a sectional view and a perspective view showing a structure of an aperture mask according to a first embodiment.

FIG. 2 is a cross-sectional view showing the manufacturing process of the aperture mask according to the first embodiment.

FIG. 3 is a cross-sectional view showing the manufacturing process of the aperture mask according to the second embodiment.

FIG. 4 is a cross-sectional view showing the manufacturing process of the aperture mask according to the third embodiment.

FIG. 5 is a cross-sectional view showing the first half of the manufacturing process of the aperture mask according to the fourth embodiment.

FIG. 6 is a sectional view showing the latter half of the manufacturing process of the aperture mask according to the fourth embodiment.

FIG. 7 is a sectional view showing the manufacturing process of the aperture mask according to the fifth embodiment.

FIG. 8 is a perspective view showing the structure of an aperture mask according to a sixth embodiment.

FIG. 9 is a schematic diagram for explaining a character projection method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate part 5 ... Heavy metal thin film 8 ... Thin film part 10 ... Aperture mask 21, 41, 51 ... Si substrate 22, 53 ... Silicon nitride film 23, 52 ... Silicon oxide film 24 ... Ti film 25 ... Pd film 26, 56 ... Electron beam resist 27, 57 ... Template 28 ... Au thin film 29 ... Photoresist 30, 60 ... Substrate opening pattern 54 ... Polycrystalline Si film 55 ... BPSG film 58 ... W film

Front page continuation (72) Inventor Nobuo Hayasaka 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Within the Corporate Research and Development Center, Toshiba Corporation (72) Inventor Gensuke Miyoshi 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Stock Incorporated Toshiba Horikawa-cho Plant (72) Inventor Kazuka Sugihara 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Incorporated, Toshiba Research and Development Center

Claims (2)

[Claims] 1. A charged particle beam drawing apparatus of a character projection system, wherein openings of a plurality of desired pattern shapes are formed, and a beam of any pattern shape is selectively irradiated with a charged particle beam. The aperture mask to be shaped is characterized in that a heavy metal thin film is used as a beam blocking and blocking film used for shaping a charged particle beam. 2. A method of manufacturing an aperture mask used in a character projection type charged beam drawing apparatus, the method comprising: forming a buffer film on one main surface of a silicon substrate; and forming a conductive film on the buffer film. A step, a step of making a template for selectively growing a heavy metal thin film on the conductive film, a step of growing a heavy metal thin film in the mold to a desired thickness, a step of removing the template, And a step of removing the back surface side of the heavy metal thin film so that an opening provided in the thin film penetrates.