JP2899542B2 - Method of manufacturing transfer mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer mask used for electron beam exposure, ion beam exposure, X-ray exposure, and the like.

[0002]

2. Description of the Related Art At present, electron beam lithography, ion beam lithography, X-ray lithography and the like have attracted attention as a manufacturing technology for a next-generation sub-half micron or quarter micron ultra-miniaturized device. It is still unclear whether it will become the mainstream technology for mass production.

[0003] Among them, electron beam exposure using an electron beam has conventionally been performed by a direct writing method (so-called single-stroke writing method) in which an exposure pattern is scanned by an electron beam (thin beam spot) to perform writing. Although this method has been put to practical use, this method is capable of drawing an ultra-fine pattern, but is not suitable for the manufacture of mass-produced LSIs such as memories due to the extremely long exposure time and low throughput. However, it was not considered that LSI mass production technology could play a leading role.

In recent years, however, various elemental patterns that repeatedly appear in an exposure pattern can be partially and collectively exposed by a transfer method using a mask, and a desired pattern can be obtained by combining these various elementary pattern transfers. A drawing method called partial batch exposure (sometimes called block exposure or cell projection exposure) has been proposed, which enables rapid pattern exposure, and has a short writing time, is mass-producible, and can draw ultra-fine patterns. For this reason, it has rapidly emerged as a next-generation LSI technology and is in the spotlight.

[0005] The mask used in this method is usually one in which a number of different elemental patterns are formed on a single mask, and the exposure using this mask involves applying an electron beam in an elemental pattern (opening). After molding and partially exposing a predetermined section (block or cell) at a time, when the transfer of one elementary pattern is completed, the electron beam is deflected and / or the mask is moved, or both are performed. Then, the next elementary pattern is transferred, and this operation is repeated to perform drawing.

[0006] A charged particle beam exposure mask used for charged particle beam exposure such as partial batch exposure using an electron beam generally has a penetrating pattern through which a charged particle beam passes through a thin film portion supported by a support frame portion. (Opening), so-called perforated mask (stencil mask; Stenci)
l mask). In other words, there is no material that transmits the charged particle beam well, and no material can be interposed in the portion that allows the charged particle beam to pass. Therefore, this portion must be penetrated. Further, when the penetrating pattern is formed on a thick substrate or the like, the charged particle beam passing therethrough is affected by the side wall of the penetrating pattern, so that accurate transfer cannot be performed. ) Must be a thin film. Also,
In order to support the thin film while maintaining planar accuracy, a support frame having a predetermined strength is required.

Here, since the above-mentioned transfer mask forms and transfers an electron beam in a through pattern (elemental pattern), various kinds of through patterns having completely different shapes and sizes are formed on the transfer mask with high dimensional accuracy. Must have been. The precision is 0.1% smaller than the design dimension in order to cope with the main use such as wiring processing of 0.20 μm or less.
Dimensional accuracy of μm or less is required. This dimensional accuracy is
Since the size of the electron beam passes through the opening pattern of the mask, the dimensional accuracy over the entire opening pattern in the mask is obtained.

A transfer mask used for such partial batch exposure and the like has been conventionally manufactured by various methods.
In general, it is manufactured by processing a silicon substrate (a commercially available silicon wafer or the like) from the viewpoint of processability and strength. Specifically, for example, the back surface of the silicon substrate is etched to form a support frame portion and a thin film portion supported by the support frame portion,
A transfer mask is formed by forming a through hole in the thin film portion.

Further, in this case, as a substrate, an SOI (S) having a structure in which _two silicon plates are bonded via an SiO ₂ layer is used.
A method of forming a silicon thin film portion using a silicon on insulator (SiO ₂ ) layer as an etching stopper layer (etching stopper layer) using a substrate (Japanese Patent Laid-Open No. Hei 6-130655).
Are mainly used.

In this case, the range in which the electron beam penetrates into the silicon substrate depends on the output (acceleration voltage).
It reaches a depth of 0-20 μm. Therefore, in order to shield the electron beam, the thickness of the silicon thin film portion needs to be 20 to 30 μm. Therefore, in order to form openings in the silicon thin film portion with high precision, it is necessary to vertically etch all kinds of opening patterns of various sizes and shapes to a depth of several tens of microns. This deep etching is called trench etching.

[0011]

However, it is very difficult to vertically etch trench patterns of various sizes from several microns to over 100 microns all at a 90 ° angle by batch etching under the same conditions.

Normally, when trench etching is performed on a pattern having an extremely different size, if the etching conditions are adjusted so that a pattern of several microns is vertically etched, the pattern size increases as the pattern size increases.
This results in tapered etching in which the bottom of the opening is narrower, and reverse taper etching in which the bottom of the opening is wider.

For example, an etching reaction product (Si
F _x, sidewall protection etching (gas pressure 50m performing trench etching while preventing the etching of the sidewalls in SiN _x or the like)
At about Torr), as the depth increases, the thickness of the protective layer formed by the reaction product attached to the side wall increases, so that taper etching is performed. In a very low temperature etching in which trench etching is performed at a low temperature (about -130 ° C., gas pressure of 20 mTorr or less) while preventing side wall etching, taper etching or reverse taper etching is performed depending on etching conditions. In very low pressure etching (gas pressure of 10 mTorr or less) in which trench etching is performed at an extremely low pressure of several mTorr, taper etching or taper etching is performed depending on etching conditions.

Here, if the silicon thin film portion forming the opening pattern is sufficiently thin (1 μm or less), the dimensions fall within the range of variation, but as described above, the silicon thin film portion is required to shield the electron beam. It cannot be thinned. Since the thickness (depth of the opening) of the silicon thin film portion is as deep as several tens of microns, even a slight taper causes a large deviation in dimensional accuracy. In addition, since the tapered portion is directly irradiated with the electron beam, the durability of the mask is reduced, and the electrons reflected on the tapered portion are scattered, thereby lowering the transfer pattern accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and enables a trench to be vertically etched regardless of a pattern size. Therefore, a transfer mask having a very high dimensional accuracy over the entire surface of the mask is manufactured. An object of the present invention is to provide a method for manufacturing a transfer mask that can be used.

[0016]

In order to achieve the above object, a method for manufacturing a transfer mask according to the present invention is a method for manufacturing a transfer mask in which an opening is formed in a thin film portion supported by a support frame. To form an etching mask layer on the substrate surface,
After patterning the etching mask layer into a desired opening shape using lithography technology, the substrate surface is trench-etched to a predetermined depth by dry etching technology using the patterned etching mask layer as a mask to form a thin film. A step of forming an opening in a portion to be a part or a thin film part, and a step of processing the back surface of the substrate by etching to form a thin film part supported by the support frame part. When patterning is performed using a lithography technique, an isolated auxiliary pattern is formed in at least a part of the openings that are tapered or reverse tapered etched under a constant etching condition.

Further, the method for manufacturing a transfer mask according to the present invention comprises:
In the method of manufacturing a transfer mask, when patterning the etching mask layer using lithography technology, an isolation auxiliary pattern is formed in at least a part of openings which are equal to or larger than a size to be vertically etched under certain etching conditions. A configuration in which the substrate surface is subjected to dry etching at a very low temperature of −130 ° C. or lower or a low pressure of 10 mTorr or lower when trench etching is performed on the substrate surface; a configuration in which the substrate is any one of an SOI substrate, a SIMOX substrate, and a silicon substrate; Alternatively, the conductive layer is formed on the transfer mask surface.

Hereinafter, the present invention will be described in detail.

In the present invention, the substrate is processed to obtain the structure shown in FIG.
A transfer mask having openings 13 formed in a thin film section 12 supported by a support frame section 11 as shown in FIG.

Here, the substrate material is Si, Mo,
From the viewpoints of chemical resistance, processing conditions, dimensional accuracy, etc., an SOI substrate, oxygen ions are implanted at a high concentration into a silicon substrate or the like, and a SIMOX (separation by implanted oxyge
n) It is preferable to use a substrate, a silicon substrate or the like. Note that when a silicon substrate doped with phosphorus or boron is used, electron conductivity and the like of the silicon substrate can be improved.

In the method of manufacturing a transfer mask according to the present invention, an etching mask layer is formed on a substrate surface (a thin film portion or a portion to be a thin film portion), and the etching mask layer is formed with a desired opening shape by lithography. When patterning into the same pattern, the isolated auxiliary pattern is formed in at least a part of the openings which are tapered or reverse tapered etched under certain etching conditions or the openings which are vertically etched under certain etching conditions. Is formed.

That is, in the present invention, the pattern of the etching mask layer for forming the opening pattern is devised. Instead of etching the entire opening as it is, the peripheral portion of the opening is defined as a line width which can be vertically etched. This is to be etched.

Here, the size to be vertically etched under constant etching conditions is determined by etching conditions such as temperature, gas used, and pressure. For example, if the etching conditions are set so that an opening having a width of 2 μm (line shape or rectangular shape) is vertically etched, an opening having a size larger than that is not vertically etched and has a tapered or reverse tapered shape (FIG. 1). ). This degree becomes more significant as the size increases. So, for example, 100μ
When an isolated auxiliary pattern of about 90 μm □ is formed in a large opening pattern of about m □, the portion to be actually etched has a width of 5 μm, and basically vertical etching is possible (FIG. 2).

The isolation auxiliary pattern means a portion that is not connected to another etching mask layer, and the silicon thin film portion in this portion is isolated from the other silicon thin film portion by trench etching. A transfer mask having a target opening from which a portion has been removed can be obtained. The obtained transfer mask has the same opening pattern as that in the case where the isolation auxiliary pattern is not provided, and does not require a special process for removal.

As an additional effect of providing the isolated auxiliary pattern, the control of the loading effect and the reduction of the microloading effect improve the stability of the process and the reproducibility of the vertical etching (including the stability of the etching apparatus).
Is improved. The loading effect is
The ratio of the area to be etched in dry etching to the entire area, the partial pattern density of the portion to be etched,
In addition, it refers to a phenomenon in which an etching shape or an etching rate changes depending on a pattern width of a portion to be etched. The microloading effect refers to a phenomenon in which the etching rate decreases as the pattern width of the portion to be etched becomes smaller and the aspect ratio (the ratio of the etching depth to the pattern width of the portion to be etched) increases.

The material and forming method of the etching mask layer are not particularly limited, and conventionally known various materials and forming methods are used.

Specifically, as the dry etching mask layer, in addition to the SiO ₂ layer, inorganic layers such as a SiC layer, a Si 3 N 4 layer, a sialon (composite mixture of Si and Al) layer, a SiON layer, a resist, a photosensitive Organic layers such as films,
Metals such as metals such as tungsten, zirconium, titanium, chromium, and nickel, alloys containing these metals, and metal layers of these metals or alloys and metal compounds of oxygen, nitrogen, carbon, and the like are used.

The dry etching mask layer can be formed by various thin film forming methods. For example, as a method for forming the SiO ₂ layer, a sputtering method, an evaporation method, a thermal oxidation method, a CV
Examples of the method include a method of forming a thin film, such as a method D, a method using SOG (spin-on-glass), photosensitive glass, and photosensitive SOG.

The patterning of the etching mask layer is performed as follows.
The patterning is performed using a lithography technique to form a desired shape. Specifically, for example, a resist is applied on the etching mask layer, a resist pattern is formed by exposure and development, and dry etching of the etching mask layer is performed using the resist pattern as a mask, and the resist pattern is transferred to the etching mask layer. I do. In addition,
Photosensitive glass or photosensitive SOG as an etching mask layer
When such a method is used, the resist process can be omitted. The resist is removed after the etching of the etching mask layer. As an etching gas for the etching mask layer (such as a SiO ₂ layer), a fluorocarbon-based gas (SF ₆
/ O ₂ , CF ₄ / O ₂ , C ₂ F ₆ / O _{2 and the} like.

In order to form an isolation auxiliary pattern on an etching mask layer, an isolation auxiliary pattern is formed in advance on a photomask (reticle or the like) for exposing a resist or the like on the etching mask layer or drawing data of an electron beam exposure apparatus. You should keep it.

The isolated auxiliary pattern may be any pattern as long as the peripheral edge of the opening can be etched with a line width that allows vertical etching, and may be a pattern as shown in FIG.

The isolated auxiliary pattern can be formed in all openings larger than the size to be vertically etched, or can be selectively provided only in an opening having a large size and a degree of taper etching.

In the present invention, the substrate surface is subjected to trench etching to a predetermined depth by a dry etching technique using the patterned etching mask layer as a mask to form an opening in a thin film portion or a portion to be a thin film portion. .

Here, the dry etching conditions include:
Etching temperature (substrate temperature), gas used, gas pressure, R
An opening of a certain size is vertically etched by adjusting these conditions.

As an etching gas used for dry etching of a silicon substrate, for example, HBr gas, Cl ₂
/ O ₂ mixed gas, SiCl ₄ / N ₂ mixed gas and the like.

The substrate temperature cannot be unequivocally determined because the optimum temperature greatly varies depending on the etching gas used. For example, when the etching gas is HBr, the substrate temperature is 20%.
When the etching gas is SiCl ₄ / SF ₆ , the temperature is preferably about -10 to 10 ° C.

The gas pressure cannot be unconditionally determined because the optimum pressure greatly differs depending on the etching gas used. For example, when the etching gas is HBr, the gas pressure is 20%.
When the etching gas is SiCl ₄ / SF ₆ , about 50 mTorr is appropriate.

When the present invention is combined with the technique of performing vertical etching at an extremely low temperature of −130 ° C. or less or an extremely low pressure of 1 mTorr or less, the taper angle can be controlled under these conditions.

In the present invention, the back surface of the substrate is processed by etching to form a thin film portion supported by the support frame. Processing of the back surface of the silicon substrate is preferably performed by wet etching from the viewpoint of manufacturing cost and processing time.

To etch the back surface of the silicon substrate, a wet etching mask layer is formed on the back surface of the substrate,
After patterning the wet etching mask layer by lithography, the back surface of the substrate may be immersed in an etchant to perform the etching process on the back surface of the substrate.

At this time, if the front and side surfaces of the substrate are affected by the etchant on the back surface of the substrate, an etching protection layer may be formed on the front and side surfaces of the substrate. The wet etching mask layer and the etching protection layer may be formed of the same material or different materials.

Examples of the etchant for the back surface of the silicon substrate include an alkaline aqueous solution such as KOH and NaOH, an alkaline aqueous solution containing alcohol and the like, and an alkaline solution such as an organic alkali.

The etching temperature is preferably set to a low temperature of 150 ° C. or less, more preferably 110 ° C. or less, in order to avoid the influence of thermal stress.
Examples of the etching method include a dipping (dipping) method.

As the wet etching mask layer formed on the back surface of the substrate, SiO ₂ , SiC, SiN, Si 3 N
4. Sialon (composite mixture of Si and Al), SiON
Such an inorganic layer can be used.

The wet etching mask layer may be made of a single metal such as tungsten, zirconium, titanium, chromium or nickel, an alloy containing these metals, or at least one of oxygen, nitrogen and carbon. A metal compound containing one or more elements can be used. These metals can be patterned by low-temperature wet etching,
Since the removal of these metals can also be performed by low-temperature wet etching at a temperature of 100 ° C. or less, breakage of the thin film portion does not occur during these processes.

Examples of the method for forming the wet etching mask layer include a thin film forming method such as a sputtering method, a vapor deposition method, and a CVD method. However, if the film quality is poor, the etchant is soaked and etching holes (etch pits) are formed in the silicon substrate. It is preferable to control the film formation conditions and the like from the viewpoint of avoiding the occurrence of such a problem, and from the viewpoint of avoiding damage such as cracks due to thermal stress or the like in the case of high-temperature film formation.

The thickness of the wet etching mask layer is
Suitably, it is in the range of 0.1 to 1 μm. If the thickness of the wet etching mask layer is less than 0.1 μm, the silicon substrate cannot be completely covered. If it exceeds 1 μm, it takes a long time to form the film and the influence of the film stress increases.

Specifically, the patterning of the wet etching mask layer is performed by applying a resist on the wet etching mask layer, forming a resist pattern by lithography, and using the resist pattern as a mask.
The wet etching mask layer is wet-etched with an etchant to perform patterning.

The etchant used for etching the wet etching mask layer is not particularly limited. For example, the SiO ₂ etchant may be buffered hydrofluoric acid or the like.
As an etchant for SiN, hot phosphoric acid or the like is used. As an etchant for titanium, an aqueous solution of 4% diluted hydrofluoric nitric acid is used. As an etchant for chromium, an aqueous solution of ceric ammonium nitrate / perchloric acid is used. Examples of the liquid include ferric chloride and the like, and examples of the tungsten etching liquid include an aqueous solution of red blood salt (potassium ferricyanide).

As the etching protection layer formed on the surface and side surfaces of the substrate, a metal layer or an inorganic layer used for the above-mentioned wet etching mask layer is used in addition to a resin layer.

Here, it is preferable to use a resin that cures at a low temperature of 200 ° C. or less as the resin layer. When the curing temperature exceeds 200 ° C., distortion and breakage of the thin film portion and the like occur due to the influence of thermal stress during the curing process. In order to more completely avoid the influence of such thermal stress, it is more preferable to use a resin that cures at room temperature.

Examples of the resin include a resin containing at least one of a fluorine resin, an ethylene resin, a propylene resin, a silicon resin, a butadiene resin, and a styrene resin.

Examples of the method for forming the resin layer on the surface and side surfaces of the substrate include a spin coating method, a dipping method, and a spraying method. The spin coating method is preferable in consideration of handling, work efficiency, and the like. The coating on the side surface of the substrate is performed, for example, by wrapping the resin around the side surface of the substrate during the initial low-speed rotation in the spin coating method.

It is appropriate that the thickness of the resin layer is 30 μm or more. If the thickness of the resin layer is less than 30 μm, the durability to the etchant and the function as a protective layer will be poor.

The resin layer can be easily formed by a spin coating method or the like without affecting other parts due to thermal stress when forming and removing the resin layer, has excellent step coverage at openings and the like, and is eroded by an etching solution. Can be completely prevented. Therefore, it contributes to stably and easily manufacturing the transfer mask.

Finally, the unnecessary layer is removed to obtain a transfer mask. Here, the wet etching mask layer and the etching mask layer are respectively removed with various etching solutions and the like, and the resin layer is removed with an organic solvent and the like.

In the present invention, any of the step of forming an opening in the upper surface of the silicon substrate and the step of processing the rear surface of the silicon substrate may be performed first. In terms of strength, the process of forming the opening first is more stable. However, in the case of using a technique (Japanese Patent Application No. 7-84733) for forming an opening after embedding a low-melting-point metal such as indium into a concave portion (window) on the back surface of the substrate developed earlier by the present applicant. The back surface may be processed.

In the present invention, a conductive layer can be formed on the surface of the above-described transfer mask or the like. This is because, in a transfer mask made of silicon alone, the silicon thin film portion in which an opening is formed as it is has poor durability against an electron beam, so that iridium (Ir), tantalum (Ta), and tungsten ( W), molybdenum (M
o), a metal layer such as gold (Au), platinum (Pt), silver (Ag), etc. is formed to improve the durability of the mask during electron beam irradiation. In addition, these metals are good conductors,
Since it has excellent electron conductivity and thermal conductivity, it contributes to prevention of beam shift due to charging (charge-up) and prevention of thermal distortion of the mask due to heat generation. Furthermore, since these metals have excellent shielding properties against electron beams and act as energy absorbers, the silicon thin film portion can be made thinner, so that the opening accuracy is improved and the effect of the opening side walls on the electron beams is reduced. Can be reduced.

The conductive layer may be formed by sputtering,
Examples of the method include a thin film formation method such as a vacuum evaporation method, an ion beam evaporation method, a CVD method, an ion plating method, an electrodeposition method, and a plating method.

Further, in the present invention, an opening can be formed by forming a conductive layer on the substrate first and then continuously dry-etching the conductive layer and the silicon thin film portion. When the opening is formed by continuously dry-etching the conductive layer and the silicon thin film portion in this manner, the opening including the conductive layer can be formed in a single step by continuous dry etching in a short time and at a high level. An accurate opening can be easily formed.

[0061]

The present invention will be described below in more detail with reference to examples.

Embodiment 1 FIG. 4 is a process explanatory view showing an example of a process for manufacturing a transfer mask of the present invention.

As shown in FIG. 4, a 1.5 μm thick SiO ₂ layer 2 was formed on the entire SOI substrate 1 (entire surface) by the CVD method (FIG. 4A).

Subsequently, a resist is applied on the SiO ₂ layer 2 on the upper surface of the substrate, and each size of 2 μm or more (5.0 μm □, 10.0 μm □, 15.0 μm □, 35.0 μm □,
0.0 μm □, 50.0 μm □, 100.0 μm □, 1
50.0 μm □, 200.0 μm □, 250.0 μm
□) Exposure was performed using a reticle in which an isolated auxiliary pattern was formed in the opening pattern, and this was developed to form a resist pattern (not shown) in which an isolated auxiliary pattern was formed in the opening pattern. The portion actually etched at each opening by the formation of the isolated auxiliary pattern is 2 μm.
Of width.

Next, using the resist pattern as a mask, the SiO ₂ layer 2 on the substrate surface is dry-etched to transfer the pattern, and the patterned SiO ₂ layer 2 having the isolated auxiliary pattern 3 in the opening pattern is formed.
(Etching mask layer) was formed (FIG. 4B). In the dry etching, the substrate temperature was 15 ° C., the etching gas was SiCl ₄ / SF ₆ / N ₂ , and the gas pressure was 30 mTorr.
r, RF output was 500 W.

After removing the resist, the silicon substrate 1 was trench-etched by dry etching using the patterned SiO ₂ layer 2 as a mask to form an opening pattern (FIG. 4C).

Subsequently, the back surface SiO ₂ layer 2 is patterned by lithography using a resist, and using this patterned back surface SiO ₂ layer 2 as a mask, ethylenediamine / pyrocatechol (catechol)
The back surface of the substrate 1 was etched into a predetermined size and shape with a mixed aqueous solution of / water to form a support frame portion and a thin film portion (FIG. 4D). At this time, the opening on the upper surface of the substrate was protected by a resin layer (not shown).

Finally, the unnecessary SiO ₂ layer 2 and the SiO ₂ layer 5 in the SOI are removed with buffered hydrofluoric acid, and an opening 13 is formed in the thin film section 12 supported by the support frame section 11. (FIG. 4E). In addition, SOI
When the SiO ₂ layer 5 was removed, the isolated auxiliary pattern 3 of the silicon thin film was also removed.

The taper angle of the opening of the obtained transfer mask was calculated by measuring the opening dimensions of the front and back sides. Table 1 shows the results.

[0070]

[Table 1]

The taper angles of the openings were almost perpendicular to 89.7 ° to 89.9 ° regardless of the pattern size. In addition, the thickness of the thin film portion was 20 μm, and the opening size of the front and back sides was shifted by about 0.5 μm at 1 °.

Example 2 A transfer mask was obtained in the same manner as in Example 1 except that the trench etching depth was changed to 15 μm.

When the taper angle of the opening of the obtained transfer mask was calculated by measuring the opening dimensions of the front and back sides, all were 89.8 ° to 89.9 ° regardless of the pattern size.
And almost vertical.

Comparative Example 1 A transfer mask was obtained in the same manner as in Example 1 except that no isolated auxiliary pattern was formed in the opening pattern.

The taper angle of the opening of the obtained transfer mask was calculated by measuring the opening dimensions of the front and back sides. Table 1 shows the results. The taper angle of the opening increases from 89.9 ° (almost vertical) to 86.8 as the pattern size increases.
° (tapered).

Example 3 In Example 1, an auxiliary auxiliary pattern of 230.0 μm square was formed only in the opening pattern of 250.0 μm square. The width of the portion to be actually etched at each opening by the formation of the isolation auxiliary pattern was 10 μm. Also,
Dry etching conditions include a substrate temperature of 20 ° C., an etching gas HBr, a gas pressure of 25 mTorr, and an RF output of 300.
W. Except for the above, a transfer mask was obtained in the same manner as in Example 1.

FIG. 5 shows the results. The taper angle of the opening of the obtained transfer mask was 89.3 °.

Comparative Example 2 A transfer mask was obtained in the same manner as in Example 3 except that no isolated auxiliary pattern was formed in the opening pattern.

FIG. 5 shows the result. 250.0μm □
The taper angle of the opening pattern was 87.6 °, and the opening dimension was shifted by 3 μm on both sides.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.

For example, a conductive layer (such as an Ir layer) is formed on the substrate surface.
Is formed, an etching mask layer having an isolated auxiliary pattern is formed thereon, and the conductive layer and the silicon thin film portion are continuously dry-etched to form an opening including the conductive layer. Vertical etching of the portion was possible.

Similar results were obtained when the back surface was processed first and the opening was processed later.

The transfer mask of the present invention can be used not only as an electron beam exposure mask but also as an ion beam exposure mask or an X-ray exposure mask.

[0084]

As described above, according to the transfer mask manufacturing method of the present invention, it is possible to perform vertical trench etching irrespective of the pattern size, and therefore, transfer having extremely high dimensional accuracy over the entire surface of the mask. A mask can be made.

According to the present invention, the formation of the isolated auxiliary pattern improves the stability of the process and the reproducibility of the vertical etching.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view for explaining taper etching.

FIG. 2 is a partially enlarged cross-sectional view for explaining vertical etching.

FIG. 3 is a plan view illustrating an aspect of an isolated auxiliary pattern.

FIG. 4 is a process explanatory view showing an example of a process for manufacturing a transfer mask according to the present invention.

FIG. 5 is a diagram showing a line width dependency of a taper angle.

[Explanation of symbols]

1 SOI substrate 2 SiO ₂ layer 3 isolated auxiliary pattern 4 intermediate SiO ₂ layer 11 the support frame portion 12 thin portion 13 opening

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (5)

(57) [Claims] 1. A method of manufacturing a transfer mask, comprising forming an opening in a thin film portion supported by a support frame portion, comprising: forming an etching mask layer on a substrate surface; and etching the etching mask layer using a lithography technique. After patterning to a desired opening shape, the substrate surface is trench-etched to a predetermined depth by dry etching using the patterned etching mask layer as a mask, and an opening is formed in a thin film portion or a portion to be a thin film portion. Forming a thin film portion supported by the support frame by etching the back surface of the substrate to form a thin film portion supported by the support frame portion. At the same time, the opening is tapered or reverse tapered etched under constant etching conditions. A method of manufacturing a transfer mask, wherein an isolation auxiliary pattern is formed in at least a part of the opening. 2. When an etching mask layer is patterned by a lithography technique, an isolated auxiliary pattern is formed in at least a part of openings which are equal to or larger than a size to be vertically etched under a predetermined etching condition. The method for manufacturing a transfer mask according to claim 1, wherein: 3. When the substrate surface is subjected to trench etching, a cryogenic temperature of −13 ° C. or less or 10 mTorr or less.
3. The method according to claim 1, wherein dry etching is performed at a low pressure of r or less. 4. The method according to claim 1, wherein the substrate is any one of an SOI substrate, a SIMOX substrate, and a silicon substrate. 5. The method for manufacturing a transfer mask according to claim 1, wherein a conductive layer is formed on the surface of the transfer mask.