JPH1070067A - X-ray exposure mask and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a beam signal intensity by positioning based on an optical heterodyne method, and to facilitate signal detection and improve an alignment accuracy by suppressing multi reflection. SOLUTION: The mask for X-ray exposure includes a mask mark region of a diffraction grating formed directly on a membrane and defined by an X-ray absorber film 3, a permeable film and an impermeable film 15 with respect to an alignment beam sequentially formed on the mask mark region. In this case, the permeable film may be a anti-reflection film, the anti-reflection film may be an alumina (Al2 O3 ) film, or the impermeable film may be a film made of tantalum (Ta) or compound thereof. In the method for fabricating the mask, with use of a stencil mask, the anti-reflection film is formed at the same time on the mask mark region for X-ray exposure using an optical heterodyne interference method for positioning and on a mask permeable window region allowing the alignment beam to pass therethrough.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an X-ray exposure mask used for manufacturing a semiconductor device and the like, and a method for manufacturing the same.

2. Description of the Related Art An alignment method utilizing optical heterodyne interferometry has been used for positioning a semiconductor wafer and an X-ray mask. The X-ray exposure mask of the present invention can be used to improve the alignment accuracy of this method.

[0003]

2. Description of the Related Art In the optical heterodyne interferometry, the amount of displacement between a semiconductor wafer and an X-ray mask is detected from the phase difference between beat signals that have undergone optical heterodyne interference.

FIG. 7 is an explanatory diagram of an alignment method using optical heterodyne interferometry. In the figure, an X-ray mask 72 is shown.
Two wavelengths (f ₁ , f ₂ ) of laser light are applied to the diffraction grating (mask mark area 74) formed on the X-ray absorption layer formed thereon and the diffraction grating (wafer mark area 75) formed on the semiconductor wafer 71.
76 and 77 are incident, and the phase difference between the optical heterodyne interference light emitted from the mask mark and the wafer mark is detected from the photoelectrically converted beat signal to perform alignment. In the figure, 73 is a mask transmission window area.

[0005] However, as shown in FIG. 8, since the X-ray mask and the semiconductor wafer are arranged close to each other,
The incident light or a part of the diffracted light generated by the incident light has multiple drawbacks on the surface of the X-ray mask and the semiconductor wafer, making the phase difference detection signal unstable and deteriorating the alignment accuracy.

Therefore, as shown in FIG. 1 (b), in the conventional method (Japanese Patent Laid-Open No. 04-372112), anti-reflection (AR) is applied to the mask transmission window region 7 of the alignment light facing the wafer mark.
By forming the film 16, the transmittance on the mask side with respect to the laser beam for position detection is improved, and the intensity of the reflected light on the mask surface is reduced. At this time, the anti-reflection film is applied to both sides of the mask substrate.

Further, by forming an opaque film (light-shielding film) 15 in the mask mark area 8 facing the X-ray photosensitive film on the wafer side, the intensity of the laser beam that passes through the mask and reaches the wafer side is reduced. Therefore, the influence of interference due to multiple reflection can be eliminated.

FIG. 9 is a diagram showing the relationship between the light-shielding film thickness and the diffraction efficiency when a light-shielding film made of titanium (Ti) is formed in a mask mark region made of a tantalum (Ta) diffraction grating pattern. In the figure, as the light-shielding film thickness increases, the intensity of the diffracted light decreases. This is because the refractive index of the X-ray absorber material (here, Ta) forming the diffraction grating pattern and the light-shielding film (metal film) are almost equal, and the grating surface is regarded as flat. This is because the more the light is blocked, the more difficult it is to distinguish the period of the diffraction grating.

As a result, it has become difficult to detect a beat signal, to be easily affected by noise, and to deteriorate the alignment accuracy. Therefore, if the light-shielding film thickness is increased, the influence of multiple interference can be suppressed, but a problem occurs in that the signal intensity decreases.

In the conventional method (Japanese Patent Laid-Open No. 04-372112), this problem occurs because one or several light-shielding films are formed in close contact with the substrate in the mask mark area.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the beat signal intensity and suppress multiple reflections in positioning by the optical heterodyne method to facilitate signal detection and improve alignment accuracy. .

[0012]

Means for solving the above problems are as follows: 1) A transparent film and an opaque film for alignment light are provided on a mask mark area composed of a diffraction grating formed by an X-ray absorber film directly on a membrane. Or 2) the X-ray exposure mask according to 1 above, wherein the transparent film is an anti-reflection film, or 3) the anti-reflection film is alumina (Al ₂ O _3). ) The said 2 which is a membrane
4) The X-ray exposure mask according to 1), wherein the opaque film is a tantalum (Ta) or tantalum compound film, or 5) The optical heterodyne interference for alignment using the stencil mask. This is achieved by a method for manufacturing an X-ray exposure mask in which an anti-reflection film is simultaneously formed on a mask mark region of the X-ray exposure mask and a mask transmission window region through which the alignment light is transmitted by using the method.

In the present invention, before forming the light shielding film in the mask mark area, a transparent film serving as an intermediate layer is applied between the membrane and the light shielding film. With this configuration, a phase difference can be generated in the transparent film, so that the intensity of diffracted light can be increased. Further, if an antireflection film material is used for the transparent film, the efficiency is improved.

FIG. 1 is an explanatory view of the structure of the present invention. Here, two conventional examples are shown side by side for comparison. Fig. 1 (a)
FIG. 3 is a cross-sectional view of a positioning portion of a conventional X-ray mask.

In the figure, 2 is a membrane made of SiC or the like, 3 is an X-ray absorber film, 7 is a mask transmission window area, and 8 is a mask mark area. FIG. 1B is a cross-sectional view of the improved conventional example described in the prior art.

In FIG. 1, reference numeral 15 denotes a light-shielding film, and 16 denotes an antireflection film. FIG. 1 (c) is a cross-sectional view of the alignment portion of the X-ray mask of the present invention.
5 is a light shielding film (opaque film). The feature in this case is X
The point is that the line absorber film 3 is formed directly on the membrane 2, and the antireflection film 12 is formed under the light shielding film 15 in the mask mark area 8.

FIG. 2 shows that the light-shielding film (Ti) is thickened to 600 °,
FIG. 9 is a diagram illustrating a change in diffraction efficiency when an antireflection film material (AR film) is used for an intermediate layer and the film thickness is changed. Anti-reflection film has anti-reflection film thickness (d = λ / 4n = 1200 °; d)
Is equal to the film thickness, λ is the wavelength = 780 nm, and n is the refractive index of the film = 1.62). The diffraction efficiency is maximized, which is more than twice that when the light shielding film is not applied.

As described above, when the anti-reflection film is applied to the mask mark area and the light-shielding film is coated thereon, not only the light is shielded to suppress the multiple reflection, but also the signal from the mask mark area is increased. be able to.

As shown in FIG. 1C, when the mask transmission window region 7 and the mask mark region 8 are simultaneously coated with an anti-reflection film with the same film thickness, the present invention can be carried out with the same number of steps as in the prior art. .

Furthermore, since any material can be used for the light-shielding film, an X-ray absorbing material such as Ta can be used, and a material that is advantageous for mask cleaning can be selected. In particular, use of Ta and its compounds is extremely advantageous in practical use because it is strong against washing.

[0021]

3 and 4 are explanatory views of a manufacturing process of an X-ray mask to which the present invention is applied. In FIG. 3A, a silicon carbide (SiC) film serving as a support substrate (membrane) 2 for an X-ray mask is formed to a thickness of about 2 μm on a silicon (Si) substrate 1 by a vapor phase growth (CVD) method.

In FIG. 3 (b), the SiC
The film 2 is removed by etching, and the surface SiC film 2 is polished and flattened. In FIG. 3 (c), the SiC
On the film 2, a Ta film 3 is formed as a heavy metal film serving as an X-ray absorber.

In FIG. 3D, the Si substrate 1 is
Then, etching of Si is performed from the back surface of the Si substrate 1.
In FIG. 4E, a resist film 5 is applied on the Ta film 3.

In FIG. 4F, electron drawing, development and etching are performed to form a pattern for the X-ray absorber on the resist film 5. In FIG. 4 (g), the resist film 5
Using the as a mask, the Ta film 3 is etched.

In FIG. 4H, after a pattern is formed on the Ta film 3, an antireflection film and a light-shielding film are applied to the alignment mark area in order to suppress the influence of the multiple reflection light generated after the alignment. Next, this step will be described in detail with reference to FIG.

FIG. 5 is an explanatory diagram of an embodiment of the present invention. In FIG. 5A, first, an anti-reflection film material is deposited on the back surface of the membrane by using a stencil mask (1) 6 having an opening corresponding to the mask transmission window region 7 and the mask mark region 8.

In FIG. 5B, anti-reflection films 9 and 10 are applied to the mask transmission window region 7 and the mask mark region 8, respectively.
Next, using a stencil mask (2) 13, an antireflection film material is deposited on the surface of the membrane (Ta film side).

In FIG. 5C, a stencil mask (2)
13, the mask transmission window area 7 and the mask mark area
8 is coated with antireflection films 11 and 12. Next, a light-shielding film is deposited on the mask mark area 8 using the stencil mask (3).

In FIG. 5D, a light shielding film 15 is formed on the antireflection film 12 in the mask mark area 8. here,
The anti-reflective coating material is determined by the refractive index of the membrane,
In the case of SiC membrane (refractive index: 2.64), alumina (A
l ₂ O ₃ ) (refractive index: 1.62 ≒ 2.64 ^1/2 ) is optimal.

The antireflection film is formed by a vapor deposition method or a sputtering method, and is formed by a metal mask (stencil mask).
Is used to partially form a film. In addition, since the antireflection film has no effect unless it is applied to both surfaces of the membrane, the antireflection film is also applied to the back surface of the membrane using a stencil mask.

Here, the partial deposition using the stencil mask is performed by using a mask due to the stress of the deposited film.
(Membrane) This is advantageous because distortion can be reduced as much as possible, and since the coating is partially applied, the influence of film deterioration due to X-ray irradiation can be reduced.

Next, also when a light-shielding film is applied to only the mask mark area using a stencil mask, the film is formed by vapor deposition or sputtering. Chromium, tantalum, tungsten or the like is effective for the light-shielding film, and light can be shielded if the thickness is about 400 mm as shown in FIG.

FIG. 6 is a diagram showing the relationship between the thickness of the Ti film and the transmittance for light having a wavelength of 780 nm.

[0034]

According to the present invention, with the same number of steps as in the prior art,
Since the intensity of the beat signal from the mask mark area can be increased and the interference effect due to multiple reflection can be suppressed, signal detection becomes easier and alignment accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of the present invention.

FIG. 2 is a diagram showing the relationship between the thickness of an antireflection film and diffraction efficiency.

FIG. 3 is an explanatory view of a manufacturing process of an X-ray mask for applying the present invention (1).

FIG. 4 is an explanatory view of a manufacturing process of an X-ray mask for applying the present invention (2).

FIG. 5 is an explanatory diagram of an embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the thickness of a light-shielding film (Ti) and transmittance.

FIG. 7 is an explanatory diagram of an alignment method using optical heterodyne interference;

FIG. 8 is an explanatory diagram of multiple reflection between a mask and a wafer.

FIG. 9 is a diagram showing the relationship between the thickness of a light-shielding film (Ti) and diffraction efficiency.

[Explanation of symbols]

 1 Silicon (Si) substrate 2 Membrane (SiC) 3 X-ray absorber film 4 Frame 5 Resist film 6 Stencil mask (1) 7 Mask transmission window area 8 Mask mark area 9, 10, 11, 12 Anti-reflection film (transparent film ) 13 Stencil mask (2) 14 Stencil mask (3) 15 Light shielding film (opaque film)

Claims (5)

[Claims] 1. A transparent film and an opaque film are sequentially formed on an alignment mark in a mask mark area formed of a diffraction grating formed by an X-ray absorber film on a membrane. X-ray exposure mask. 2. The X-ray exposure mask according to claim 1, wherein said transparent film is an anti-reflection film. 3. The X-ray exposure mask according to claim 2, wherein said anti-reflection film is an alumina (Al ₂ O ₃ ) film. 4. The X according to claim 1, wherein said opaque film is a tantalum (Ta) or tantalum compound film.
Line exposure mask. 5. An anti-reflection film is simultaneously formed on a mask mark region of an X-ray exposure mask using optical heterodyne interference for alignment and a mask transmission window region through which alignment light is transmitted, using a stencil mask. A method for producing an X-ray exposure mask, characterized by the following.