JPH0656831B2 - Lithographic mask structure manufacturing method and thin film manufacturing method - Google Patents

Description

The present invention relates to a mask structure for lithography.

[Prior Art] X-ray lithography is characterized by straightness, incoherence, and
Due to its low diffractive property, it has many advantages over conventional lithography using visible light and ultraviolet light, and is attracting attention as a powerful means of submicron lithography.

X-ray lithography has many advantages over lithography with visible light or ultraviolet light, but lacks X-ray source power, resist low sensitivity, alignment difficulty, mask material selection and processing methods are difficult. From the
It has the drawbacks of low productivity and high cost, and its commercialization is delayed.

Taking a mask for X-ray lithography among them, in visible light and ultraviolet light lithography, a glass plate and a quartz plate have been used as a mask material holder (that is, a light transmitting body), but in X-ray lithography, The wavelength of light that can be used is 1 to 200 Å, and conventional glass plates and quartz plates have large absorption in this X-ray wavelength range and the thickness must be 1 to 2 mm.
These are not suitable as the material of the mask material holder for X-ray lithography because they do not sufficiently transmit rays.

Since the X-ray transmittance generally depends on the density of a substance, an inorganic substance or an organic substance having a low density is being studied as a material for the mask material holder for X-ray lithography. Examples of such a material include beryllium (Be), titanium (Ti),
Examples include inorganic substances such as simple substances of silicon (Si) and boron (B) and their compounds, or organic substances such as polyimide, polyamide, polyester, and parylene.

In order to actually use these substances as a material for the mask material holder for X-ray lithography, it is necessary to make them thin to increase the X-ray transmission amount as much as possible. In this case, it is required to form it to a thickness of several tens of μm or less. Therefore, for example, when forming a mask material holding thin film composed of an inorganic thin film and a composite film thereof, a thin film of silicon nitride, silicon oxide, boron nitride, silicon carbide or the like is formed on a silicon wafer having excellent flatness by vapor deposition or the like. A method of removing the silicon wafer by etching later has been proposed.

On the other hand, as a mask material for X-ray lithography (that is, an X-ray absorber) which is held on the holding thin film as described above, a thin film of a substance having a high density such as gold, platinum, tungsten, tantalum, copper or nickel is generally desirable. Is 0.5-1μ
A thin film having a thickness of m is preferable. In such a mask material, for example, a thin film of the high-density material is uniformly formed on the X-ray transparent film, a resist is applied, and a desired pattern is drawn on the resist by an electron beam, light, or the like. After that, a desired pattern is formed by using a method such as etching.

However, in the conventional X-ray lithography as described above, the X-ray transmittance of the mask material holding thin film is low, and therefore the mask material holding thin film needs to be made considerably thin in order to obtain a sufficient X-ray transmission amount. However, there was a problem that its manufacture became difficult.

[Object of the Invention] The present invention has been made in view of the above-described conventional techniques, and an object of the present invention is to provide a mask structure for X-ray lithography having a mask material holding thin film having good X-ray transparency.

SUMMARY OF THE INVENTION According to the present invention, an object as described above is formed of a film containing aluminum nitride as a main component on a substrate by a plasma CVD method, or at least a laminated film containing aluminum nitride as a main component. And a step of providing an annular holding substrate for holding a peripheral portion of the mask holding thin film, and a method of manufacturing a mask structure for lithography.

Further, according to the present invention, the above object is to provide a mask holding on a substrate by a plasma CVD method, which is made of a film containing aluminum nitride as a main component, or at least a laminated film containing aluminum nitride as a main component. Lithography comprising a step of forming a thin film, a step of selectively forming a mask on the mask holding thin film, and a step of providing an annular holding substrate for holding the peripheral portion of the mask holding thin film. And a method of manufacturing a mask structure.

Further, according to the present invention, a plasma CVD method is performed on the substrate surface using a gas containing at least an aluminum element and a gas containing a nitrogen element to obtain a thin film containing aluminum nitride as a main component on the substrate surface. A method for producing a thin film is provided.

[Example] "A film containing aluminum nitride as a main component" in the present invention
Is formed by the plasma CVD method. This "film containing aluminum nitride as a main component" may be made of aluminum nitride only, or may be a film containing a small amount of another element or compound in aluminum nitride. Examples of such a small amount of contained substances include H, N, C, O, etc., which are the components in the gas when performing the plasma CVD method.

Mask holding thin film in the present invention (mask material holding thin film)
May be a single layer of "a film containing aluminum nitride as a main component" (hereinafter, simply referred to as "aluminum nitride film"), or a laminate of an aluminum nitride film and another inorganic film and / or organic film. It may consist of a film.

As the inorganic substance forming the laminated film, one having at least a film forming property and an X-ray transmitting property can be used. Examples of such inorganic substances include boron nitride, silicon nitride, silicon oxide, silicon carbide, titanium and the like.

As the organic substance forming the laminated film, one having at least film forming property and X-ray transmissive property can be used. Examples of such organic substances include polyimide, polyamide, polyester, parerin (trade name, manufactured by Union Carbide Co.).

The laminated film may be composed of two or three layers of an aluminum nitride film and an inorganic film and / or an organic film, or two layers of at least one of the aluminum nitride film and the inorganic film and / or the organic film. It is also possible to use three or more layers as a whole by using the above.

The thickness of the mask material holding thin film in the present invention is not particularly limited and can be set to an appropriate thickness, but it is advantageous to set it to, for example, about 2 to 20 μm.

The mask structure of the present invention can be obtained by holding the peripheral portion of the mask material holding thin film with an appropriate annular holding substrate. Examples of such a holding substrate include glass, silicon, quartz, phosphor bronze, brass, iron, nickel, and stainless steel, but are not limited to these.

The mask structure of the present invention also includes a mask holding thin film provided with a thin film-shaped mask material. As the mask material, for example, gold, platinum, tungsten, tantalum, copper,
Examples thereof include nickel, but are not limited to these. The mask material may be provided on one surface of the holding thin film, or may be patterned into a desired pattern.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 As shown in FIG. 1 (a), a PIQ solution (polyimide precursor, manufactured by Hitachi Chemical Co., Ltd.) was spin-coated on one surface of a circular silicon wafer 1 having a diameter of 10 cm, and then 50-35.
Curing was performed at 0 ° C. for 4 hours to form a polyimide film 2 having a thickness of 1.5 μm.

Next, as shown in FIG. 1 (b), the polyimide film 2
The silicon wafer 1 on which is formed is set in a plasma CVD apparatus (manufactured by Nichiden Anelva), the temperature of the silicon wafer is kept at 240 ° C., and triethyl aluminum (A
l (CH ₃ ) ₃ ) while bubbling hydrogen (H ₂ ) gas in ammonia (NH ₃ ) gas and hydrogen gas (gas flow rate of 11 SCCM each) at 13.56 MHz, 4 W high-frequency power, internal pressure of about 1 Torr. Then, the aluminum nitride film 3 having a thickness of about 4 μm was formed on the polyimide film 2 by the plasma CVD method. The film formation rate at this time is about 200Å
/ Min, and the required time was about 3 hours.

Next, as shown in FIG. 1 (c), an epoxy adhesive 5 is applied to one surface of a ring frame (made by Pyrex, inner diameter 7.5 cm, outer diameter 9 cm, thickness 5 mm) which is an annular holding substrate.
Is applied, and the aluminum nitride film 3 is applied to the adhesive application surface.
Glued the faces.

Next, as shown in FIG. 1 (d), the ring frame 4
A notch was made in the aluminum nitride film 3 and the polyimide film 2 along the outer periphery of.

Next, as shown in FIG. 1 (e), ultrasonic waves were applied in an aqueous solution containing a surfactant (sodium alkylbenzene sulfonate) to separate and remove the silicon wafer 1.

Next, as shown in FIG. 1 (f), the polyimide film 2 was removed with a hydrazine-based solvent. During the solvent treatment, a tar-based paint was applied on the aluminum nitride film 3 in order to protect it, the polyimide film 2 was removed, and then the tar-based paint layer was removed with acetone.

Thus, a mask structure for X-ray lithography in which the peripheral portion of the mask material holding thin film made of the aluminum nitride film 3 is held by the ring frame 4 which is an annular holding substrate was obtained.

It was confirmed that no pinholes were observed in the aluminum nitride film 3 of the mask structure obtained in this example, and that the internal stress was small.

Example 2: A photoresist C is formed on the aluminum nitride film 3 which is a mask material holding thin film of the mask structure obtained in Example 1.
MS (chloromethyl polystyrene, manufactured by Toyo Soda Co., Ltd.)
Was formed to a thickness of about 1 μm.

Next, a mask pattern was drawn using an electron beam drawing device, and then prescribed processing was performed to obtain a resist pattern.

Next, tantalum (Ta) was vapor-deposited to a thickness of 0.5 μm on the resist pattern using an electron beam vapor deposition machine.

Next, the resist was removed using a remover to obtain a tantalum film pattern serving as a mask material.

Thus, an X-ray lithography mask structure was obtained in which the peripheral portion of the mask material holding thin film made of the aluminum nitride film on which the tantalum film pattern mask material was formed was held by the ring frame that was the annular holding substrate.

Example 3: The same process as in Example 1 was performed except that the polyimide film 2 was not removed in the process of Example 1.

Thus, an X-ray lithography mask structure was obtained in which the peripheral portion of the mask material holding thin film made of a laminated film of the aluminum nitride film and the polyimide film was held by the ring frame which was the annular holding substrate.

It was confirmed that no pinhole was observed in the laminated film of the aluminum nitride film and the polyimide film, which are the mask material holding thin films of the mask structure obtained in this example, and the internal stress was small.

Example 4 As shown in FIG. 2A, a silicon oxide film 12 having a thickness of 1 μm was formed on both surfaces of a circular silicon wafer 11 having a diameter of 10 cm.

Next, as shown in FIG. 2 (b), after spin-coating the PIQ solution on the silicon oxide film 12 on one surface side of the silicon wafer 11, curing is performed at 50 to 350 ° C. for 4 hours to obtain a thickness of 2 μm. Then, the polyimide film 13 was formed.

Next, as shown in FIG. 2C, the silicon oxide film 1
2 and the silicon wafer 11 on which the polyimide film 13 was formed were set in the plasma CVD apparatus used in Example 1, the temperature of the silicon wafer was kept at 250 ° C., and aluminum trichloride (AlCl ₃ ) was replaced with nitrogen (N ₂ ). Plasma bubbling in ammonia gas and nitrogen gas (gas flow rate of 10 SCCM each) with high frequency power of 13.56 MHz and 20 W at an internal pressure of about 1 Torr while bubbling with gas.
Then, an aluminum nitride film 14 having a thickness of about 3 μm was formed on the polyimide film 13 by the method. The film forming rate at this time is about 3
It was 000Å / min, and the required time was about 10 minutes.

Next, as shown in FIG. 2D, a tar-based coating layer 15 for protection was formed on the aluminum nitride film 14.

Next, as shown in FIG. 2 (e), the exposed central portion of the circular shape of the silicon oxide film 12 having a diameter of 7.5 cm was removed using a mixed solution of ammonium fluoride and hydrofluoric acid. At this time, in order to leave the ring-shaped silicon oxide film 12, a layer 16 of apiezon wax (made by Shell Chemical Co., Ltd.) for protection is formed on that portion, and after removing the central portion of the silicon oxide film, The wax layer 16 was removed.

Next, as shown in FIG. 2 (f), electrolytic etching (current density 0.2 A / dm ² ) was performed in a 3% hydrofluoric acid aqueous solution to expose the exposed diameter of 7.5 c of the silicon wafer 11.
The circular central part of m was removed.

Next, as shown in FIG. 2G, the exposed portion of the silicon oxide film 12 was removed using a mixed solution of ammonium fluoride and hydrofluoric acid.

Next, as shown in FIG. 2 (h), a ring frame (made by Pyrex, inner diameter 7.5c) that constitutes the annular holding substrate.
m, outer diameter 9 cm, thickness 5 mm) 17 is coated with an epoxy adhesive 18, and the surface of the silicon wafer 11 opposite to the polyimide film 13 and aluminum nitride film 14 formation surface is coated on the adhesive application surface. After adhesion, the tar-based paint layer 15 was removed with acetone.

Thus, the polyimide film 13 and the aluminum nitride film 14
The peripheral portion of the mask material holding thin film made of a laminated film of
A mask structure for X-ray lithography held by No. 1 was obtained.

The polyimide film 13 and the aluminum nitride film 14, which are the mask material holding thin films of the mask structure obtained in this example.
It was confirmed that no pinhole was observed in the laminated film of and the internal stress was small.

Example 5: In the same manner as in Example 4, a silicon oxide film was formed on both surfaces of a silicon wafer, and a polyimide film and an aluminum nitride film were formed on one surface thereof.

Next, a 0.5 μm thick gold (Au) film as a mask material was uniformly formed on the aluminum nitride film using a resistance heating vapor deposition machine.

Then, a photoresist AZ-1350 is uniformly formed on the gold film.
(Manufactured by Shipley) was applied to a thickness of 0.5 μm.

Next, a master mask was brought into close contact with the resist, the resist was baked using deep ultraviolet light, and then prescribed processing was performed to obtain a positive resist pattern for the master mask.

Next, the gold film was etched using an iodine (I ₂ ) based gold etchant to obtain a gold film pattern as a positive-type mask material for the master mask.

Next, the resist was removed with a ketone solvent.

Next, a tar-based paint layer for protection was formed on the aluminum nitride film having the gold film pattern formed thereon.
The same process was performed.

Thus, for X-ray lithography in which the peripheral portion of the mask material holding thin film made of a laminated film of the polyimide film and the aluminum nitride film on which the gold film pattern mask material is formed is held by the ring frame as the annular holding substrate and the silicon wafer. A mask structure was obtained.

EFFECTS OF THE INVENTION According to the present invention as described above, aluminum nitride used as a constituent element of a mask material holding thin film has a high X-ray transmittance and a visible light transmittance (the optical density at a thickness of 1 μm is about 0.
1), low thermal expansion coefficient (3 to 4 × 10 ⁻⁶ / ° C.), high thermal conductivity, and good film-forming property, and the like, the following effects can be obtained.

(1) Since the aluminum nitride film has a high X-ray transmittance and a relatively high X-ray transmission amount can be obtained even if it is relatively thick, the mask material holding thin film can be easily and favorably manufactured.

(2) Since the aluminum nitride film has a good film-forming property, a mask material holding thin film made of an extremely thin film can be manufactured, whereby the X-ray transmission amount can be increased and the printing throughput can be improved.

(3) Since the aluminum nitride film has a high visible light transmittance, it can be easily and accurately aligned visually by using visible light in X-ray lithography.

(4) Since the coefficient of thermal expansion of the aluminum nitride film is almost the same as the coefficient of thermal expansion (2 to 3 × 10 ⁻⁶ / ° C.) of the silicon wafer printing substrate in X-ray lithography, it is possible to perform baking with extremely high precision. Become.

(5) Since the aluminum nitride film has high thermal conductivity, it is possible to prevent a temperature rise due to X-ray irradiation, and it is particularly effective when baking in a vacuum.

Further, in the present invention, since the aluminum nitride film is formed by the plasma CVD method, it has excellent film characteristics without pinholes and small internal stress. Further, since a high film forming rate can be obtained in forming the film, a high quality mask structure for X-ray lithography can be obtained in a relatively short time.

[Brief description of drawings]

1 (a) to (f) and FIGS. 2 (a) to (h) are views showing a manufacturing process of a mask structure for X-ray lithography according to the present invention. 1, 11: Silicon wafer 2, 13: Polyimide film 3, 14: Aluminum nitride film 4, 17: Ring frame 5, 18: Adhesive 12: Silicon oxide film

Claims (5)

[Claims] 1. A step of forming a mask holding thin film made of a film containing aluminum nitride as a main component or at least a laminated film containing at least aluminum nitride as a main component on a substrate by a plasma CVD method, and the mask. And a step of providing an annular holding substrate for holding the peripheral portion of the holding thin film, and a method for manufacturing a mask structure for lithography comprising: 2. A step of forming a mask holding thin film made of a film containing aluminum nitride as a main component, or at least a laminated film containing at least aluminum nitride as a main component on a substrate by plasma CVD, and the mask. A method of manufacturing a mask structure for lithography, comprising: a step of selectively forming a mask on a holding thin film; and a step of providing an annular holding substrate for holding a peripheral portion of the mask holding thin film. 3. The step of selectively forming a mask is performed by forming a resist pattern on a mask holding thin film, subsequently applying a mask material in a thin film shape on the resist pattern, and then removing the resist. A method of manufacturing a mask structure for lithography according to claim 2. 4. The step of selectively forming a mask comprises applying a thin film-shaped mask material on one surface of a mask-holding thin film, and subsequently forming a resist on the thin-film mask material applied on the entire surface of the mask-holding thin film. The method for manufacturing a mask structure for lithography according to claim 2, which is performed by forming the pattern and then etching the mask material through the resist pattern. 5. Plasma C is formed on the surface of the substrate by using a gas containing at least an aluminum element and a gas containing a nitrogen element.
A method for producing a thin film, which comprises subjecting the substrate surface to a VD method to obtain a thin film containing aluminum nitride as a main component.