JPH0481855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a mask structure for X-ray lithography.

[Conventional technology] X-ray lithography has many advantages over conventional lithography using visible light and ultraviolet light, based on the straightness, non-coherence, and low diffraction properties unique to X-rays. , is attracting attention as a powerful means of submicron lithography.

Although X-ray lithography has many advantages over lithography using visible light and ultraviolet light, it suffers from insufficient power of the X-ray source, low sensitivity of the resist,
Due to difficulties in alignment, selection of mask materials, and processing methods, there are drawbacks such as low productivity and high cost, and practical application has been delayed.

Looking at masks for X-ray lithography, in visible light and ultraviolet lithography, glass plates and quartz plates have been used as mask holders (i.e., light transmitting bodies); The available wavelength of light is 1 in
200 Å, and conventional glass plates and quartz plates have large absorption in this X-ray wavelength range and have to be thick, 1 to 2 mm, so they do not transmit enough X-rays. is unsuitable as a material for a mask holder for X-ray lithography.

Since X-ray transmittance generally depends on the density of a substance, low-density inorganic and organic materials are being considered as materials for mask holders for X-ray lithography. Examples of such materials include inorganic materials such as beryllium (Be), titanium (Ti), silicon (Si), and boron (B) alone and their compounds, and organic materials such as polyimide, polyamide, polyester, and parylene. It will be done.

In order to actually use these materials as materials for mask holders for X-ray lithography, it is necessary to make them into thin films in order to maximize the amount of X-ray transmission. In this case, it is required to form the film to a thickness of several tens of micrometers or less. For this reason, for example, when forming a mask holder made of an inorganic thin film or a composite film thereof, silicon nitride, silicon oxide, boron nitride, silicon carbide, etc. are deposited on a silicon wafer with excellent flatness. A method has been proposed in which the silicon wafer is removed by etching after forming a thin film.

On the other hand, as a mask for X-ray lithography (i.e., an X-ray absorber) held on the above-mentioned holder, it is generally preferable to use a thin film made of a high-density material such as gold, platinum, tungsten, tantalum, copper, or nickel. is preferably a thin film with a thickness of 0.5 to 1 μm. Such a mask is made by, for example, uniformly forming a thin film of the high-density material on the X-ray transparent film, applying a resist, and drawing a desired pattern on the resist using an electron beam, light, etc.
Thereafter, a desired pattern is created using means such as etching.

However, in conventional X-ray lithography as described above, the X-ray transmittance of the mask holder is low, so in order to obtain a sufficient amount of X-ray transmission, the mask holder must be made considerably thinner. There was a problem in that it was difficult to manufacture, and in particular, it was difficult to obtain sufficient flatness of the mask holder.

There was a problem.

[Object of the Invention] In view of the above-mentioned prior art, the present invention provides a mask structure for X-ray lithography consisting of a mask holder and a mask frame that have good X-ray transparency and sufficient flatness. The purpose is to provide.

[Summary of the Invention] According to the present invention, the above object is to form a mask holder made of aluminum nitride or a mask holder made of a laminate containing at least aluminum nitride on a substrate, and to attach a mask to the mask holder. This is achieved by a method for manufacturing a mask structure for X-ray lithography, characterized in that the substrate is removed after adhering the frame.

[Example] The mask holder in the mask structure obtained by the present invention may be made of a single layer of aluminum nitride, or may be made of a laminate of aluminum nitride and other inorganic and/or organic substances.

As the inorganic substance constituting the laminate, one having at least film-forming properties and X-ray transparency can be used. Examples of such inorganic materials include boron nitride, silicon nitride, silicon oxide, silicon carbide, and titanium.

As the organic substance constituting the laminate, one having at least film-forming properties and X-ray transparency can be used. Examples of such organic materials include polyimide, polyamide, polyester, paryrin (manufactured by Union Carbide), and the like.

The laminate may be composed of two or three layers of aluminum nitride and an inorganic material and/or an organic material, or may be composed of two or more layers of aluminum nitride and at least one of an inorganic material and/or an organic material to form a total of three layers. It may be made up of more than one layer.

The thickness of the mask holder in the mask structure obtained by the present invention is not particularly limited and can be set to an appropriate thickness, for example, 2 to 2.
Advantageously, the thickness is approximately 20 μm.

In the mask structure obtained by the present invention, the mask holder may or may not be patterned.

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

Example 1 As shown in FIG. 1a, after spin-coating PIQ liquid (polyimide precursor, manufactured by Hitachi Chemical Co., Ltd.) on one side of a circular silicon wafer 1 with a diameter of 10 cm,
1.5μm after curing for 4 hours at 50-350℃
A thick polyimide film 2 was formed.

Next, as shown in Fig. 1b, an aluminum (Al) target, a mixed gas of argon (Ar):nitrogen (N ₂ ) = 1:1, and a gas pressure of 5 x 10 ^-3 were prepared using the reactive sputtering method. Torr, discharge power 200W,
An aluminum nitride film 3 having a thickness of 3 μm was formed on the polyimide film 2.

Next, as shown in Fig. 1c, an epoxy adhesive 5 is applied to one side of the ring frame (manufactured by Pyrex, inner diameter 7.5 cm, outer diameter 9 cm, thickness 5 mm) 4, and the adhesive-applied surface is The aluminum nitride film 3
I glued the sides together.

Next, as shown in FIG. 1d, cuts were made in the aluminum nitride film 3 and the polyimide film 2 along the outer periphery of the ring frame 4.

Next, as shown in FIG. 1e, the silicon wafer
was separated and removed.

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

In this way, an X-ray lithography mask structure in which the aluminum nitride film 3 was fixed to the ring frame 4 was obtained.

Example 2 The aluminum nitride film 3 of the mask structure obtained in Example 1 was coated using a resistance heating evaporator.
A gold (Au) film with a thickness of 0.5 μm was uniformly formed.

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

Next, a master mask was brought into close contact with the resist, and after the resist was baked using deep ultraviolet light, 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 positive gold film pattern with respect to the master mask.

Next, the resist was removed using a ketone solvent.

In this way, an X-ray lithography mask structure was obtained in which an aluminum nitride film on which a gold film pattern was formed was fixed to a ring frame.

Example 3 The same steps as in Example 1 were performed except that the polyimide film 2 was not removed.

In this way, the laminate of polyimide film and aluminum nitride film is fixed to the ring frame.
A mask structure for line lithography was obtained.

Example 4 In the process of Example 1, after forming the aluminum nitride film 3, a 0.5 μm thick gold (Au) film was uniformly formed on the aluminum nitride film using a resistance heating vapor deposition machine.

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

Next, a master mask was brought into close contact with the resist, and after the resist was baked using deep ultraviolet light, 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 positive gold film pattern with respect to the master mask.

Next, after removing the resist with a ketone solvent,
Epoxy adhesive was applied to one side of the ring frame (manufactured by Pyrex, inner diameter 7.5 cm, outer diameter 9 cm, thickness 5 mm) in the same manner as in Example 1, and aluminum nitride with the gold film pattern was applied to the adhesive coated surface. The membrane surface was glued.

Thereafter, in the same manner as in Example 1, cuts were made in the aluminum nitride film and polyimide film along the outer periphery of the ring frame, and ultrasonic waves were applied in an aqueous solution containing a surfactant (sodium alkylbenzene sulfonate) to form a silicon wafer. was separated and removed.

In this way, an X-ray lithography mask structure was obtained in which a laminate of a polyimide film and an aluminum nitride film on which a gold film pattern was formed was fixed to a ring frame.

Example 5 On both sides of a circular silicon wafer with a diameter of 10 cm
A silicon oxide film with a thickness of 1 μm was formed.

Next, using a reactive sputtering method, an aluminum (Al) target was placed on the silicon oxide film on one side of the silicon wafer, and a mixed gas of argon (Ar):nitrogen (N ₂ )=1:1 was used at a gas pressure of 8×10 ^{- 3} Torr,
After forming a 2 μm thick aluminum nitride film with a discharge power of 300 W, a 2 μm thick boron nitride film was formed on the aluminum nitride film by the same sputtering method except that a boron nitride target was used.

Next, a ring frame was bonded in the same manner as in Example 1, and the same steps as in Example 1 were performed to separate and remove the silicon wafer with the silicon oxide film.

In this way, the laminate of aluminum nitride film and boron nitride film is fixed to the ring frame.
A mask structure for line lithography was obtained.

Example 6 In the process of Example 5, after forming the boron nitride film, a 1 μm film was further formed by reactive sputtering.
The same steps as in Example 5 were performed except for forming an aluminum nitride film with a thickness of m.

In this way, an X-ray lithography mask structure was obtained in which a laminate having a structure of aluminum nitride film; boron nitride film; and aluminum nitride film was fixed to a ring frame.

[Effects of the Invention] According to the method of the present invention as described above, the mask holder can be fixed to the mask frame with sufficient flatness, so the mask holder can be thinned and
The amount of radiation transmitted can be increased.

Furthermore, aluminum nitride used as a component of the mask holder of the mask structure manufactured by the method of the present invention as described above has high X-ray transmittance and visible light transmittance (optical density of about 0.01 at 1 μm thickness),
Since it has features such as a low coefficient of thermal expansion (3 to 4 x 10 ^-6 /°C), high thermal conductivity, and good film forming properties, the following effects can be obtained.

(1) Aluminum nitride has a high X-ray transmittance, and even if it is relatively thick, a relatively high amount of X-ray transmission can be obtained, so that the mask structure can be manufactured easily and favorably.

(2) Since aluminum nitride has good film forming properties, it is possible to manufacture a mask structure with a mask holder made of an extremely thin film, which increases the amount of X-ray transmission and improves the throughput of baking. can.

[Brief explanation of drawings]

1a to 1f are diagrams showing the steps of the method of the invention. 1: Silicon wafer, 2: Polyimide film,
3: Aluminum nitride film, 4: Ring frame,
5: Adhesive.

Claims (1)

[Claims] 1. A mask holder made of aluminum nitride or a mask holder made of a laminate containing at least aluminum nitride is formed on a substrate, and after a mask frame is adhered to the mask holder, the substrate is removed. A method for manufacturing a mask structure for X-ray lithography, characterized in that: 2. The method for manufacturing a mask structure for X-ray lithography according to claim 1, which comprises forming a mask on a mask holder.