JPH04346214A - Mask for x-ray exposure and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a reflection-type X-ray mask with a high reflection factor and a reduced exposure time by eliminating a problem of reduction in reflection factor due to roughening on a reflecting surface of a multilayer film by a conventional method for manufacturing a reflection-type X-ray mask. CONSTITUTION:A focusing energy beam is emitted to a multilayer film 2 of a space portion of a mask pattern, thus machining to a state where no X-rays are reflected, in a reflection-type mask for X-ray exposure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray exposure mask used for X-ray reduction exposure used, for example, in the manufacturing process of semiconductors and the like.

0002

2. Description of the Related Art Lithography using short-wavelength X-rays can achieve high resolution, which is theoretically impossible with ultraviolet rays. In such X-ray lithography, a transmission type X-ray mask is used as an X-ray reduction exposure mask, and the light transmitted through the mask is formed into an image by a subsequent optical system;
There is a reflective X-ray mask that forms an image using light reflected from a mask.

[0003] Transmission type X-ray masks are made by forming a desired pattern with an X-ray absorbing material on a membrane made of a material that transmits X-rays relatively well, but the membrane is very fragile and difficult to handle. However, there are problems such as distortion occurring in the pattern position due to the internal stress of the membrane and absorbing material and heating by X-rays. Reflection type X-ray masks have come to be used as a solution to these problems of transmission type X-ray masks.

Conventionally used reflective X-ray masks include:
As shown in FIG. 8, the X-ray absorber 16 provided on the X-ray reflective multilayer film 2 uniformly formed on the substrate 3 is manufactured by performing dry etching or wet etching to form a predetermined pattern. (a), or (b) is manufactured by removing the multilayer film in the non-reflective portion of the pattern by dry etching or wet etching.

[0005]

[Problem to be solved by the invention] In the X-ray reflecting mirror,
The rougher the surface/interface of a multilayer film, the lower the reflectance of X-rays, so the surface/interface of a multilayer film used in a reflective X-ray mask must be extremely smooth.

However, in the manufacturing process of conventional reflective X-ray masks, an etching process of the resist or the multilayer film itself is essential, and in this etching process, the smooth reflective surface of the multilayer film becomes rough. There is a problem that the X-ray reflectance decreases. Furthermore, if the reflectance of the exposure mask is low, the time required for exposure will be longer.
There are problems such as poor throughput.

The present invention solves the above problems and uses a manufacturing method that prevents the reflective surface of the multilayer film from becoming rough.
The aim is to obtain a line mask.

[0008]

[Means for Solving the Problem] In the reflective mask for X-ray exposure according to the invention described in claim 1, an X-ray reflective multilayer film formed on a substrate has an X-ray reflective part and a non-reflective part. In the reflective mask for X-ray exposure in which a mask pattern consisting of the following was formed, the non-reflective portion of the pattern was formed of the multilayer film itself processed so as not to reflect X-rays.

Further, in the method for manufacturing a reflective mask for X-ray exposure according to the second aspect of the invention, the X-ray film formed on the substrate is
The non-reflective portions of the mask pattern are formed by irradiating a linearly reflective multilayer film with a focused energy beam.

0010

[Function] The present invention provides an X-ray mask pattern in which the multilayer film in the X-ray non-reflecting portion (hereinafter referred to as space portion) is processed so that it does not instantly reflect X-rays by irradiation with a focused energy beam. Since it is a reflective mask, the reflectance of the multilayer film surface in the reflective portion is as high as it was immediately after film formation. In other words, only the area irradiated with the focused energy beam will instantly undergo diffusion and recrystallization between the two types of materials that make up the multilayer film, causing destruction of the multilayer film periodic structure (interference effect) and the creation of scattering surfaces on the surface. The reflectance is processed to be extremely low.

[0011] Therefore, the surface of the multilayer film in the reflective portion remains smooth without being affected by thermal diffusion, and its X-ray reflectance hardly decreases compared to immediately after film formation. In addition, in this way, the X
By using a line exposure mask, it is also possible to shorten the exposure time.

0012

[Embodiment] A reflective mask for X-ray exposure and a method of manufacturing the same according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a diagram showing a method of manufacturing a reflective mask for X-ray exposure according to an embodiment of the present invention.

In FIG. 1, a focused energy beam 1 is irradiated onto a space in a pattern of a multilayer film 2 formed on a substrate 3, thereby instantaneously destroying the periodic structure of the multilayer film and reducing surface roughness. A mask pattern is formed. FIG. 2 shows an example in which a laser beam is used as the focused energy beam. A multilayer film reflector 4 formed by depositing a molybdenum (Mo)/silicon (Si) multilayer film with a periodic length of 88 Å and a laminated number of 50 layers on a Si substrate is
-Place it on Y stage 5.

Laser light 7 from a YAG laser (wavelength: 1.06 μm) 6 is focused onto the multilayer film by a lens 8 to a diameter of 1 μm, and the X-Y stage 5 is moved at a constant speed while keeping the laser output constant. By doing so, a line and space pattern with a pitch of 1 μm is formed. That is, in the pattern space portion, by such local heat treatment using laser light, a compound of Mo and Si of a multilayer film is formed, the periodic structure is destroyed, and X-rays cannot be reflected.

The reflectance of the reflective X-ray mask manufactured in this example and the reflective X-ray mask manufactured by the conventional method was determined at wavelength 12.
Measurements and comparisons were made using 4 Å X-rays. As a result, as shown in FIG. 5, the reflectance of the conventional reflective X-ray mask was 20%, while the reflective
The reflectance of the line mask was 30%, which is the same as the reflectance of the multilayer film immediately after film formation.

FIG. 6 shows an exposure experiment conducted using the reflective X-ray mask 4 according to this embodiment. A parallel X-ray beam 12 with a wavelength of 124 Å obtained by spectroscopy of synchrotron radiation is
X-ray 1 incident on the ray mask 4 at an angle of 45° and reflected
The image No. 3 was transferred onto a Si wafer 14 coated with a positive type PMMA resist. The direction of the pattern is perpendicular to the reflective surface (paper surface). The transfer onto the wafer 14 was 0.8 μm in the pattern portion and 0.6 μm in the space portion. This value is in agreement with the expected value, and furthermore, the exposure time was shortened to two-thirds of that in the case of a conventional reflective X-ray mask.

Next, FIG. 3 shows an embodiment in which an ion beam is used as the focused energy beam. Vacuum container 9
Inside, a multilayer film reflecting mirror 4 similar to that shown in FIG. 2 is placed on an XY stage 5, and the ion beam 10 is focused onto the multilayer film to a diameter of 1 μm. A line-and-space pattern with a pitch of 1 μm is formed by moving the XY stage 5 at a constant speed while keeping the accelerating voltage and accelerating current of the ion beam 10 constant.

When the reflectance of the reflective X-ray mask according to the embodiment shown in FIG. 3 was measured using X-rays with a wavelength of 124 Å, it was 27%, which is almost lower than the reflectance of the multilayer film immediately after deposition. do not have. Furthermore, as a result of the exposure experiment shown in Figure 6,
The transfer onto the wafer 14 was 0.8 μm for the pattern portion and 0.6 μm for the space portion, which matched the expected values, and the exposure time was shortened to 2/3 of that using a conventional reflective X-ray mask. .

FIG. 4 shows an embodiment in which an electron beam is used as the focused energy beam. Inside the vacuum container 9, a multilayer mirror 4 similar to that shown in FIG.
An electron beam 11 was focused on it to form a line-and-space pattern with a pitch of 0.5 μm.

The reflectance of the reflective X-ray mask according to the embodiment shown in FIG. 4 was measured using X-rays with a wavelength of 125 Å and was 30%, which is the same as the reflectance of the multilayer film immediately after deposition. Ta. Furthermore, as a result of conducting the exposure experiment shown in FIG.
The upward transfer was 0.4 μm for the pattern portion and 0.3 μm for the space portion, which matched the expected values, and the exposure time was shortened to 2/3 of that for a conventional reflective X-ray mask.

In the embodiments described above with reference to FIGS. 2 to 4, the work holder is cooled with liquid nitrogen to prevent heat diffusion. In addition, during the actual process, as shown in FIG. 7, the image of the X-rays 13 reflected by the reflective X-ray mask 4 is reduced to about 1/10 by an optical system 15 composed of a multilayer mirror. Transfers fine patterns.

[0022]

[Effects of the Invention] As explained above, the present invention is an X-ray reflective mask in which the multilayer film in the space portion of the mask pattern is irradiated with a focused energy beam so that it does not momentarily reflect X-rays. , the reflectance of the multilayer film surface in the reflective portion is as high as it was immediately after the film was formed. In other words, only the part irradiated with the focused energy beam instantaneously causes the two types of materials that make up the multilayer film to diffuse and recrystallize, causing the periodic structure of the multilayer film to break and surface roughness to increase, resulting in a decrease in reflectance. Processed into an extremely small size.

Therefore, the surface of the multilayer film in the reflective area is not affected by thermal diffusion, etc., and the surface smoothness immediately after film formation is maintained, and its X-ray reflectance is almost the same as that immediately after film formation. Does not decrease. Further, by using an X-ray exposure mask with a higher reflectance than ever before, it is also possible to shorten the exposure time.

Furthermore, if a laser that can be used even in the atmosphere is used, a mask can be created with a simple device, and costs can be reduced. Furthermore, if there is a machining error in a space part of a mask pattern produced using a conventional method, it is also possible to apply the method of the present invention and correct the mask by irradiating the pattern error part with a focused energy beam. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a reflective X-ray mask according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for manufacturing a reflective X-ray mask using laser light, which is an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a reflective X-ray mask manufacturing method using an ion beam, which is an embodiment of the present invention.

FIG. 4 is an explanatory diagram of a method for manufacturing a reflective X-ray mask using an electron beam, which is an embodiment of the present invention.

FIG. 5 is a diagram showing the X-ray reflectance at a wavelength of 124 Å of a reflective X-ray mask according to an embodiment of the present invention and a conventional mask.

FIG. 6 is a configuration diagram of an exposure experiment system using a reflective X-ray mask according to an embodiment of the present invention.

FIG. 7 is a configuration diagram of a reduction projection exposure apparatus using a reflective X-ray mask and a multilayer mirror.

FIG. 8 is an explanatory diagram of a conventional reflective X-ray mask.

[Explanation of symbols]

1: Focused energy beam 2: Multilayer film 3: Substrate 4: Reflective X-ray mask 5: X-Y stage 7: Laser light 9: Vacuum container 10: Ion beam 11: Electron beam 12: X-ray beam 13: Reflected X-ray 14:Si wafer

Claims (2)

[Claims] 1. A reflective mask for X-ray exposure, in which a mask pattern consisting of an X-ray reflective part and a non-reflective part is formed on an X-ray reflective multilayer film formed on a substrate, in which the non-reflective part of the pattern is A reflective mask for X-ray exposure, characterized in that the reflective portion is the multilayer film itself processed so as not to reflect X-rays. 2. A reflective mask for X-ray exposure, characterized in that a non-reflective part of a mask pattern is formed by irradiating an X-ray reflective multilayer film formed on a substrate with a focused energy beam. Manufacturing method.