JPH0656830B2 - Mask structure for lithography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a lithographic mask structure.

<Prior Art> X-ray lithography is a straight line characteristic of X-ray, non-interfering
Due to its low diffractive property, it has many advantages over conventional lithographic methods using visible light and ultraviolet light, and is attracting attention as a powerful means of submicron lithographic methods.

Although X-ray lithography has many advantages over lithography by visible light or ultraviolet light, X-ray source power shortage, resist low sensitivity, alignment difficulty, mask material selection and processing method Because of the difficulty of
It has the drawbacks of low productivity and high cost, and its commercialization is delayed.

Taking a lithographic mask as an example, a glass plate and a quartz plate have been used as a mask holder (that is, a light transmitting body) in visible light and ultraviolet light lithographic, but in X-ray lithographic, The wavelength of light that can be used is from 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 as thick as 1-2 mm. Since they are not sufficiently transmitted, they are unsuitable as materials for the mask holder for X-ray lithography.

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 holder for X-ray lithography. Examples of such a material include inorganic substances such as beryllium (Be), titanium (Ti), silicon (Si) and boron (B) simple substances and their compounds, or organic substances such as polyimide, polyamide, polyester and parylene. To be

In order to actually use these substances as materials for the mask holder for X-ray lithography, it is necessary to make them thin so as 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 holder made of an inorganic thin film and its composite film, silicon nitride, silicon oxide, boron nitride, silicon carbide, etc. are deposited on a silicon wafer having excellent flatness by vapor deposition or the like. It has been proposed to remove the silicon wafer by etching after forming the thin film.

On the other hand, as a mask for X-ray lithography (that is, an X-ray absorber) held on the above-mentioned holder, generally, a substance having a high density such as gold, platinum, tungsten, tantalum,
A thin film of copper, nickel, or the like, preferably a thin film having a thickness of 0.5 to 1 μm is preferable. In such a mask, 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 created using a means such as etching.

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

Further, generally, the mask holder is used as a mask structure bonded to one flat end surface of a mask frame which is ring-shaped and has flat both end surfaces. The thickness of the adhesive layer may be uneven depending on the method of applying the adhesive when the mask holder is adhered, and further, the protruding portion of the mask holder after adhesion from the mask frame may be cut off. At that time, it is difficult to keep the flatness of the mask holder sufficiently because the mask holder is turned up.

Thus, it cannot be said that sufficient accuracy is achieved in conventional lithography.

<Purpose of the Invention> In view of the above-mentioned conventional techniques, the present invention is a lithographic mask in which a mask holder having good X-ray transparency is adhesively supported on a ring-shaped mask frame with sufficient planarity. The purpose is to provide a structure.

<Outline of the Invention> According to the present invention, the above-described object is to provide a film whose mask holder contains aluminum, nitrogen, and oxygen (hereinafter, referred to as Al-N).
-O-based film) or at least Al-N-
Achieved by a lithographic mask structure comprising a laminated body including an O-based film, wherein the mask holder and the mask frame are bonded at a position lower than the uppermost flat end surface of the mask frame. To be done.

<Example> Specific shapes of the mask structure of the present invention are shown in FIGS. 1 (a) and 1 (b). FIG. 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 the figure, 2 is a mask holder, and the peripheral portion of the mask holder 2 is supported on the upper end surface of the ring-shaped mask frame 3.

The mask holder 2 in the mask structure of the present invention is made of Al-N.
It may be composed of a single layer of —O-based film, or may be made of Al.
It may be composed of a laminate of a -N-O-based film and another inorganic and / or organic material.

As the inorganic substance forming the laminate, one having at least a film forming property and an X-ray transmitting property can be used. Examples of such an inorganic material include aluminum nitride, boron nitride, silicon nitride, silicon oxide, silicon carbide,
Titanium etc. are illustrated.

Among these, aluminum nitride is particularly preferable because it has features such as high X-ray transmittance and visible light transmittance, low thermal expansion coefficient, high thermal conductivity, and good film forming property.

As the organic substance that constitutes the laminated body, at least a film-forming body and one having X-ray transparency can be used. Examples of such organic substances include polyimide, polyamide, polyester, parerin (manufactured by Union Carbide Co.) and the like.

The laminate may be composed of two or three layers of an Al-N-O-based film and an inorganic material and / or an organic material, or A
Two or more layers of at least one of an l-N-O-based film and an inorganic substance and / or an organic substance may be used to form a total of three or more layers.

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 advantageous to set it to, for example, about 2 to 20 μm.

In the mask structure of the present invention, the mask material may not be provided on the mask holding body 2, the mask material may be provided on one surface, or the mask 1 having a desired pattern is formed. May be.

As the mask 1, for example, gold, platinum, nickel, palladium, rhodium, indium, tungsten, tantalum,
A thin film of about 0.5 to 1 μm thick such as copper is used.

In the mask structure of the present invention, the uppermost flat end surface 3a of the mask frame 3 is not coated with an adhesive for adhering the mask holder, and the sloped surface 3b that intersects the flat end surface 3a at an angle θ is formed. Only the adhesive 4 is applied. The angle θ is not particularly limited as long as it is a value exceeding 0 degree, but it is preferably 5 to 90 degrees, more preferably 5 to 60 degrees, and most preferably 5 to 60 degrees.
It is 30 degrees.

The mask frame 3 in the mask structure of the present invention includes, for example, silicon, glass, quartz, phosphor bronze, brass, nickel,
Made of stainless steel, etc.

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

Hereinafter, the present invention will be described 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, an outer surface of the uppermost flat end face is formed with a slope that intersects the flat end face at an angle of 15 degrees. 3) A polyimide which is isotropically stretched through the adhesive 4 by applying an epoxy adhesive 4 to the slope The film (thickness 7 μm) 2-1 was adhesively fixed to the mask frame 3, and the polyimide film protruding from the mask frame 3 was cut off.

Next, as shown in FIG. 2 (b), using heat electron impact type ion plating rolling section aluminum (Al) Tagetsuto, argon (Ar): nitrogen _(N 2): oxygen (O
₂ ) = 1: 3: 0.1 mixed gas, gas pressure 3 × 10 ⁻⁴ T
Orr, discharge power of 400 W, and a film thickness of 3 μm of Al—N—O on the polyimide film 2-1 at a deposition rate of about 10 Å / sec.
The system film 2-2 was formed.

Next, as shown in FIG. 2C, a gold (Au) film 1 ′ having a thickness of 0.5 μm is uniformly formed on the Al—N—O based film 2-2 by using a resistance heating vapor deposition machine. Formed.

Next, as shown in FIG. 2 (d), a photoresist AZ-1350 (manufactured by Shipley Co.) 5 was uniformly applied on the gold film 1'to a thickness of 0.5 .mu.m.

Next, as shown in FIG. 2 (e), a master mask is brought into close contact with the resist, the resist is baked using deep ultraviolet light, and then a prescribed process is performed to make a positive type mask for the master mask. A resist pattern was obtained.

Next, as shown in FIG. 2 (f), the gold film 1'was etched using an iodine (I ₂ ) type gold etchant to obtain a positive type gold film pattern for the master mask.

Next, the resist is removed with a ketone solvent to form a mask 1 having a gold film pattern. As shown in FIG. 2 (g), the polyimide film 2-1 and the Al—N—O film 2-2 are formed. And a mask 1 on the mask holder.
A mask structure for lithographic formation, in which is formed, is obtained.

Example 2 After the Al—N—O based film 2-2 was formed in the process of Example 1, the exposed portion of the polyimide film 2-1 was further removed by reactive ion etching in oxygen plasma, and then Al—N. The same steps as in Example 1 were performed except that the gold film 1 ′ was formed on the —O-based film 2-2.

Thus, a mask structure for lithography having an Al—N—O-based film mask holder and having a mask formed on the mask holder was obtained.

Example 3: After the polyimide film protruding from the mask frame in Example 1 was cut off, aluminum (Al) target, argon (Ar): nitrogen (N ₂ ): oxygen (O ₂ ) was formed on the polyimide film by the reactive sputtering method. ₂ ) = 1: 1: 1
0.5 μm mixed gas, gas pressure 5 × 10 ⁻³ Torr, discharge power 150 W, film formation rate about 15 Å / min, 1 μm thick Al
A -NO film was formed.

Next, a boron nitride film having a thickness of 2 μm was formed on the Al—N—O based film by the same sputtering method except that the boron nitride target was used.

Next, a mask having a gold film pattern is formed on the boron nitride film in the same manner as in Example 1, and the polyimide film and Al—N are used.
A lithographic mask structure having a laminated body composed of an —O-based film and a boron nitride film as a mask holder was obtained.

Example 4 In Example 1, after the polyimide film protruding from the mask frame was cut off, aluminum oxynitride (7Al ₃ O ₇ : was formed on the polyimide film by the reactive sputtering method.
3AlN) target, gas of argon (Ar): nitrogen (N ₂ ) = 1: 1, gas pressure of 5 × 10 ⁻³ Torr,
Discharge power 200W, film formation rate about 10Å / min 1μm
A thick Al-N-O based film was formed.

Then, the aluminum (A
l) Target, Argon (Ar): Nitrogen (N ₂ ) =
An aluminum nitride film having a thickness of 0.5 μm was formed with a mixed gas of 1: 1 at a gas pressure of 8 × 10 ⁻³ Torr and a discharge power of 200 W.

Next, the same steps as in Example 1 were performed except that the exposed portion of the polyimide film was removed by reactive ion etching in oxygen plasma and then the gold film was formed on the aluminum nitride film.

Thus, a lithographic mask structure was obtained in which a laminated body composed of an Al—N—O-based film and an aluminum nitride film was used as a mask holder, and a mask was formed on the mask holder.

The mask holder forming the mask structure obtained in this example was particularly excellent in overall performance such as X-ray transparency, visible light transparency, thermal conductivity, and film formability.

Example 5: Al—N—O on the upper slope 3b of the ring frame 3 of the lithographic mask structure obtained in Example 1.
A pressing ring 10 was further adhered onto the system film 2-2 via an adhesive 9 as shown in FIG. A of the presser ring 10
The bonding surface with the l-N-O film 2-2 is formed parallel to the upper slope 3b of the ring frame 3.

In the lithographic mask structure of this example,
The ring frame 3 of the mask holder is supported by applying pressure between the ring frame 3 and the pressing ring 10 to support them.
Support can be made stronger.

In the above embodiment, the slanted surface 3b is formed outside the uppermost flat end surface 3a of the ring-shaped mask frame 3 and intersects the uppermost flat end surface 3a at a constant angle, and the slanted surface 3b is bonded. The mask structure of the present invention is not limited to this.

FIG. 4 (a) is a central longitudinal sectional view of the mask structure according to the present invention for showing another shape of the mask frame 3, and FIG.
FIG. 3B is a plan view of the mask frame 3. Here, on the outer side of the uppermost flat end surface 3a of the mask frame 3, there is formed an inclined surface 3b that is smoothly continuous with the uppermost flat end surface 1a, and the inclined surface 3b is bonded.

FIG. 5 is a central longitudinal sectional view of a mask structure according to the present invention for showing still another shape of the mask frame 3. Here, a slope 3b is formed outside the uppermost flat end surface 3a of the mask frame 3 at a right angle to the uppermost flat end surface 3a, and further outside the slope 3b than the uppermost flat end surface 3a. The plane 3c is formed at a lower position, and the plane 3c
Adhesion is made in.

<Effects of the Invention> According to the present invention as described above, the Al—N—O-based film used as a constituent element of the mask holder has high X-ray transmittance and visible light transmittance (about 1 μm thick optical density is about 100 μm). 0.1),
It has features such as low coefficient of thermal expansion (3 to 4 × 10 ⁻⁶ / ° C.), high thermal conductivity, and good film-forming property.

Further, the mask structure of the present invention as described above has a feature that the mask holder and the mask frame are bonded to each other outside the mask holding plane of the mask holder (at a position lower than the plane).

In the present invention, the following effects can be obtained due to the above effects.

(1) The mask holder is supported on the uppermost flat end surface of the mask frame without using an adhesive, and the uppermost flat end surface of the mask frame is subjected to ultra-planar processing (for example, 2 μm or less).
The mask holder is not affected by uneven thickness of the adhesive layer caused by uneven coating at the time of applying the adhesive, and by curling up caused by cutting off the mask peripheral portion of the mask holder. A high-performance mask holder having high line transmittance and visible light transmittance and excellent thermal conductivity can maintain good flatness equivalent to that of the uppermost flat end surface of the mask frame.

(2) Since the Al-N-O-based film has a good film-forming property, it is possible to manufacture a mask structure having a mask holder made of an extremely thin film, which increases the X-ray transmission amount and the throughput of printing. Can be improved.

Furthermore, since the mask holder has a good flatness as described above, the gap between the mask structure and the object to be exposed can be easily set, and the throughput can be further improved.

(3) Since the Al—N—O type film has a high visible light transmittance,
In X-ray lithography, alignment can be easily and accurately visually performed using visible light.

Furthermore, since the mask holder has good flatness as described above, the error in the gap value between the mask structure and the object to be exposed becomes small, and the alignment accuracy can be further improved.

(4) The coefficient of thermal expansion of the Al—N—O-based film is almost the same as the coefficient of thermal expansion (2 to 3 × 10 ⁻⁶ / ° C.) of the silicon wafer-baked substrate in X-ray lithography. Baking is possible.

(5) The thermal conductivity of the Al-N-O-based film is high, and the mask holder and the mask frame are in direct contact with each other at the position closest to the X-ray irradiation region without the use of an adhesive. The heat is conducted in the film (mask holder) in a short time and is further transmitted to the mask frame, so that the temperature rise can be prevented. In particular, the effect is great when baking in a vacuum.

[Brief description of drawings]

FIG. 1 (a) is a vertical sectional view of the mask structure of the present invention.
FIG. 1 (b) is a plan view of the mask frame. 2 (a) to 2 (g) are views showing a manufacturing process of the mask structure of the present invention. FIG. 3 is a vertical cross-sectional view of the mask structure of the present invention. FIG. 4 (a) is a vertical sectional view of the mask structure of the present invention, and FIG. 4 (b) is a plan view of the mask frame. FIG. 5 is a vertical sectional view of the mask structure of the present invention. 1: Mask 2-1: Polyimide film 2-2: Al-N-O type film 3: Mask frame 3a: Top flat end face 3b: Slope 3c: Plane 4: Adhesive 5: Photoresist

Claims (2)

[Claims] 1. A lithographic mask structure in which a mask holder is supported on a mask frame, wherein the mask holder is made of a film containing aluminum, nitrogen and oxygen, or contains at least aluminum, nitrogen and oxygen. A mask structure for lithography, comprising a laminate containing a film containing the mask frame, wherein the mask holder and the mask frame are bonded to each other at a position lower than the uppermost flat end face of the mask frame. . 2. The lithographic mask structure according to claim 1, wherein a mask is formed on the mask holder.