JPS61140942A - Mask structure for lithography - Google Patents

Abstract

PURPOSE:To enhance X-ray transmittance by using a mask holder composed of a laminate of aluminum nitride alone or a combination contg. it and bonding the holder to a mask frame below the uppermost flat face of the frame. CONSTITUTION:The slope of the ring frame 3 is coated with an epoxy adhesive 4 and an isotropically stretched polyimide film 2-1 is bonded and fixed to the slope, and on this film the aluminum nitride film 2-2 is formed. Further, a golden film 1' is uniformly formed on the film 2-2, and the film 1' is uniformly coated with a photoresist 5. A master mask is brought into close contact with the photoresist 5 and it is exposed to far UV rays to obtain a positive type resist pattern. The golden film 1' is etched with the 12 type gold etchant to obtain a positive type golden film pattern, the resist is removed with a ketone type solvent, and the mask structure for X-ray lithography is thus formed on the laminate of the polyimide film 2-1 and the aluminum nitride film 2-2.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to lithographic mask structures.

[Prior art] X-ray lithography has the inherent straightness, non-coherence,
Based on its low diffraction properties, it has many advantages over conventional lithography using visible light and ultraviolet light, and 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 also suffers from insufficient power of the X-ray source, low sensitivity of the resist, difficulty in alignment, and difficulty in selecting mask materials and processing methods. Because of that, etc.
It has the disadvantages of low productivity and high cost, and its 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 wavelength of light that can be produced is said to be 1 to 200 people, 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, making it difficult to absorb X-rays. Since they are not sufficiently transparent, they are unsuitable as materials for mask holders for X-ray lithography.

Since X-ray transmittance generally depends on the density of a substance, inorganic and organic materials with low density are being considered as materials for mask holders for X-ray lithography. Examples of such materials include inorganic materials such as beryllium (Be), titanium (Tt), 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 substances as materials for mask holders for X-ray lithography, it is necessary to make them into thin films in order to maximize the X-ray transmission i). In this case, it is required to form the film to a thickness of several tens of pm 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,
A method has been proposed in which a thin film of poron nitride, silicon carbide, or the like is formed and then the silicon wafer is removed by etching.

On the other hand, the X-ray lithography mask (that is, the X-ray absorber) held on the above-mentioned holder is generally made of high-density materials such as gold, platinum, tungsten, tantalum, copper, nickel, etc. !Preferably 0.5-I
Such a mask, which is preferably made of a thin film with a thickness of gm, can be made by, for example, forming a thin film of the high-density material uniformly on the X-ray transparent film, applying a resist, and exposing the resist to an electron beam or light. A desired pattern is drawn by etching or the like, and then a desired pattern is created by etching or other means.

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

Furthermore, the above-mentioned mask holder is generally used as a mask structure that is bonded to one flat end surface of a mask frame that is ring-shaped and has both flat end surfaces. Depending on the method of applying the adhesive when adhering the mask holder, the thickness of the adhesive layer may become uneven, or even when the part of the mask holder that protrudes from the mask frame after adhesion is removed. Since the mask holder tends to curl up, it has been difficult to maintain sufficient flatness of the mask holder.

Thus, it cannot be said that sufficient precision is necessarily achieved in conventional X-ray lithography.

[Object of the Invention] In view of the above-mentioned prior art, the present invention provides a lithography mask structure in which a mask holder having good X-ray transparency is adhesively supported on a ring-shaped mask frame with sufficient flatness. The purpose is to provide.

[Summary of the Invention] According to the present invention, the following object is that the mask holder is made of aluminum nitride aluminum or is made of a laminate containing at least aluminum nitride, and the uppermost flat end surface of the ring-shaped mask frame This is achieved by a lithography mask structure characterized in that the mask holder and the ring-shaped mask frame are bonded at a lower position.

[Example] The specific shape of the mask structure of the present invention is shown in Fig. 1(a) and (
1(a) is a central longitudinal sectional view of the mask structure, and FIG. 1(b) is a plan view of the mask frame. In FIG. 0, 2 is a mask holder; The peripheral part of the mask holder 2 is connected to the end surface 1 of the ring-shaped mask frame 3.
− is supported.

The mask retaining body 2 in the mask structure of 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.1. %.

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 substances include poron 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, and valerin (manufactured by Union Carbide).

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 also consist of layers north of the layer.

The thickness of the mask holder 2 in the mask structure of the present invention is not particularly limited and can be set to an appropriate thickness, but it is convenient to set it to about 2 to 20 g.m, for example.

In the mask structure of the present invention, it goes without saying that the mask l of a desired pattern may be formed on the mask holder 2.

As the mask 1, for example, a thin film of gold, platinum, nickel, palladium, rhodium, indium, tungsten, tantalum, copper, etc. with a thickness of about 0.5 to 17 zm is used.

In the mask structure of the present invention, the uppermost flat end surface 3a of the mask frame A3 is not coated with an adhesive for adhering the mask holder, and the slope 3b intersects with the outside of the flat end surface 3a at an angle θ. Adhesive 4 is applied only to. There is no particular restriction on the angle θ as long as it exceeds 0 degrees, but
Preferably it is 5 to 90 degrees, more preferably 5 to 60 degrees, optimally 5 to 30 degrees.

The mask frame 3 in the mask structure of the present invention is made of, for example, silicon, glass, quartz, phosphor bronze, brass, nickel, stainless steel, or the like.

Further, as the adhesive 4 in the mask structure of the present invention,
For example, solvent-based adhesives (butadiene-based synthetic rubber adhesives,
chloroprene-based synthetic rubber adhesives, etc.), solvent-free adhesives (
epoxy adhesives, cyanoacrylate adhesives, etc.) are used.

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

Example 1: As shown in FIG. 2(a), a ring frame (made of Pyrex, inner diameter 7.5 cm, outer diameter 9 cm, thickness 5 mm,
However, on the outside of the top flat end surface, a slope that intersects with the flat end surface at an angle of 15 degrees is formed.) Epoxy adhesive 4 was applied to the sloped part of 3, and was stretched isotropically through the adhesive 4. Polyimide film C thickness 7 m) 2-1 to mask frame 3
The polyimide film protruding from the mask frame 3 was cut off.

Next, as shown in FIG. 2(b), using the reactive vanta method, an aluminum (A1) target, a mixed gas of argon (Ar):nitrogen (N2) = 1:1,
With gas pressure 5XLO-3To-rr and discharge power 200W,
An aluminum nitride film 2-2 having a thickness of 3 m was formed on the polyimide film 2-1.

Next, as shown in FIG. 2(C), 0.5 g of gold (Au) fl@t' with a thickness of m is uniformly applied to the aluminum nitride film 2-2 using a resistance heating leather bonding machine. Formed.

Next, as shown in FIG. 2(d), a photoresist AZ-1350 (manufactured by Shipley) 5 was uniformly coated on the gold film l' to a thickness of 0.5/j and m.

Next, as shown in FIG. 2(e), a master mask is brought into close contact with the resist L, and after the resist is baked using deep ultraviolet light, a prescribed process is performed to form a positive resist onto the master mask. I got the pattern.

Next, as shown in FIG. 2(f), the gold nl2t' was etched using an iodine (2) etchant to obtain a positive gold film pattern on the master mask.

Next, the resist is removed with a ketone solvent to form a mask l consisting of a gold film pattern, and as shown in FIG. 2(g), a polyimide film 2-1 and an aluminum nitride film 2-2 are laminated. A mask structure for X-ray phosphorography was obtained, in which the body was used as a mask holder and a mask 1 was formed on the mask holder.

Example 2: Aluminum nitride ff5!2- in the process of Example 1
After forming the aluminum nitride film 2-2, the exposed portion of the polyimide film 2-1 was removed by reactive ion etching in oxygen plasma, and then gold [
The same steps as in Example 1 were performed except for forming 1'.

In this way, a mask structure for X-ray lithography was obtained in which the aluminum nitride film was used as a mask holder and a mask was formed on the mask holder.

Example 3: An adhesive 9 was further applied on the aluminum nitride Il' 22-2 of the ring frame 3 of the ring frame 3 of the X-ray lithography mask structure obtained in Example 1 as shown in FIG. The presser ring 10 was attached via the . The adhesive surface of the holding ring IO with the aluminum nitride film 2-2 is formed parallel to the L-portion slope 3b of the ring frame 3.

In the X-ray lithography mask structure of this embodiment, the support of the mask holder to the ring frame 3 is made stronger by applying pressure between the ring frame 3 and the holding ring 10. be able to.

In the above embodiment, a slope 3b is formed on the outside of the top flat end surface 3a of the ring-shaped mask frame 3, and the slope 3b intersects with the top F end surface 3a at a certain angle, and the bonding is performed on the slope 3b. However, the mask structure of the present invention is not limited thereto.

FIG. 4(a) is a central vertical sectional view of a mask structure according to the present invention to show another shape of the mask frame 3, and FIG. 4(b) is a plan view of the mask frame 3. Here, a slope 3b smoothly connected to the top flat end surface 1a is formed on the outside of the top flat end surface 3a of the mask frame 3, and bonding is performed on the slope 3b.

FIG. 5 is a central vertical cross-sectional view of the mask structure according to the present invention to show still another shape of the mask frame 3. FIG. Here, a slope 3b that is perpendicular to the top flat end surface 3a is formed on the outside of the top flat end surface 3a of the mask frame 3, and further outside the slope 3b is the top flat end surface 3a.
A plane 3C is formed at a lower position than the plane 3C.
Adhesion is made at C.

[Effects of the Invention] According to the present invention as described above, aluminum nitride used as a component of the mask holder has high X-ray transmittance and visible light transmittance <(optical density of lum thickness of about 0. 01
), the coefficient of thermal expansion is low (3~4x f o −'/”C
) - has features such as high thermal conductivity and good film formability, so 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 a 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, thereby increasing the amount of X-ray transmission and improving the baking throughput. can.

(3) Since aluminum nitride has a high transmittance to visible light, 7-line alignment can be easily and accurately performed visually using visible light in X-ray lithography.

(4) The thermal expansion coefficient of aluminum nitride is the thermal expansion coefficient of the silicon wafer baked substrate in X-ray lithography (
Since the value is approximately the same as 2 to 3X 10-6 /'0), extremely high precision printing is possible.

(5) Since aluminum nitride has high thermal conductivity, temperature rise due to X-ray irradiation can be prevented, which is particularly effective when baking in vacuum.

Further, according to the mask structure of the present invention, the adhesion between the mask holder and the mask frame is performed outside the mask holding plane of the mask holder. The flatness of the mask holding surface of the mask holder is not adversely affected by the removal of the mask holder, and the mask holder can maintain good flatness.

[Brief explanation of drawings]

FIG. 1(L) is a longitudinal cross-sectional view of the mask structure of the present invention,
FIG. 1(b) is a plan view of the mask frame. FIGS. 2(a) to 2(g) are diagrams showing the manufacturing process of the mask structure of the present invention. FIG. 3 is a longitudinal sectional view of the mask structure of the present invention. FIG. 4(a) is a longitudinal cross-sectional view of the mask structure of the present invention,
FIG. 4(b) is a plan view of the mask frame. FIG. 5 is a longitudinal sectional view of the mask structure of the present invention. 1: Mask 2-1: Polyimide film 2-2: Aluminum nitride film 3: Mask frame 3a: Top flat end surface 3b = slope 3C: Plane 4: Adhesive 5: Photoresist agent Patent attorney Seki Yamashita Taira 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) In a lithography mask structure in which a mask holder is supported by a ring-shaped mask frame, the mask holder is made of aluminum nitride or is made of a laminate containing at least aluminum nitride, and the ring-shaped mask frame A lithography mask structure, wherein the mask holder and the ring-shaped mask frame are bonded to each other at a position lower than the uppermost flat end surface of the mask structure. (2) The lithography mask structure according to claim 1, wherein a mask is formed on the mask holder.