JPH01175736A - Reflective mask - Google Patents

Abstract

PURPOSE:To obtain a reflective mask with which soft X rays or the like can be applied positive to a substrate surface and which has low thermal expansion properties, high heat conduction properties, thermal stability and low strain and facilitates high contrast by a method wherein at least two types of materials whose optical constants are different are alternately built up to form multilayer films and a reflective part and nonreflective parts are composed of the multilayer films. CONSTITUTION:A reflective part 10 which reflects soft X rays or/and vacuum ultraviolet rays is provided on the surface of a substrate 1 which does not reflect soft X rays or/and vacuum ultraviolet rays. Further, a pattern composed of nonreflective parts 16 which prevents soft X rays or/and vacuum ultraviolet rays from being reflected is provided on the reflective part 10. At that time, at least two types of material whose optical constants are different are alternately built up to form multilayer films and the reflective part 10 and the nonreflective parts 16 are composed of the multilayer films. For instance, a PMMA layer is formed on the surface of the reflective part 10 as a resist layer and patterned by EB lithography. Then 13 layers of Si films and Mo films are alternately built up on the surface so as to make the thicknesses of the Si films and Mo films 71Angstrom , 37Angstrom , 31Angstrom ,..., 36Angstrom , 32Angstrom , 36Angstrom and 33Angstrom respectively alternately by sputtering evaporation. Then the resist layer is removed to form multilayer film nonreflective parts 31 on the reflective part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a reflective mask, and particularly to soft
This invention relates to a reflective mask using a pattern consisting of a reflective part and a non-reflective part having a predetermined reflectance for vacuum ultraviolet rays (hereinafter referred to as "soft X-rays, etc.").

(Prior Art) Conventionally, exposure masks for semiconductor manufacturing equipment using soft X-rays, etc. have been made by using gold (A
u) Various transmission masks have been proposed in which non-transmissive patterns are formed from absorbing materials such as tantalum (Ta).

On the other hand, in Japanese Patent Application Laid-open No. 53-139469, Bragg
A reflective mask for X-ray lithography that uses diffraction conditions to form a pattern made of a single crystal or completely amorphous material different from the substrate on the surface of a substrate made of a single crystal or completely amorphous material. is proposed.

Due to the nature of reflection in conventional reflective masks, soft X-rays, etc. must be incident obliquely on the substrate surface, which increases the mask area and makes it difficult to polish the substrate and improve the flatness of the mask surface. difficult to maintain.

Further, there are other problems such as it becomes difficult to support the mask with high accuracy and the overall size of the apparatus increases.

In addition, in a reflective mask in which a pattern consisting of a non-reflective portion is formed using an absorber on a reflective portion consisting of a multilayer film,
Soft X-rays, etc. can be incident at an angle close to normal incidence, but the thickness of the non-reflective part must be made sufficiently thick so that the soft X-rays, etc. do not reach the reflective part formed below the non-reflective part. There was a need.

In this case, in an exposure apparatus for semiconductor manufacturing in which it is difficult to irradiate a reflective mask with soft X-rays or the like perpendicularly, the reflective surface 2o has a shadow area 23 due to the non-reflective portion 21, as shown in FIG. This was not pleasant.

Incidentally, in FIG. 2, reference numeral 24 denotes a reflective section made of a multilayer film.

(Problems to be Solved by the Invention) The present invention provides a method for transferring a pattern to be transferred onto a predetermined surface of a substrate onto a reflective portion made of a multilayer film in which at least two types of materials are alternately laminated. By providing a structure with a non-reflective part, soft X-rays, etc. can be used with normal incidence on the substrate surface, and a thermally stable, low distortion, high contrast with low thermal expansion and high thermal conductivity can be used. The object of the present invention is to provide a reflective mask for lithography using easily obtained soft X-rays and/or vacuum ultraviolet rays.

(Means for solving the problem) A reflective part that reflects soft X-rays and/or vacuum ultraviolet rays is provided on the substrate surface that is non-reflective for soft X-rays and/or vacuum ultraviolet rays, and When providing a pattern consisting of a non-reflective part that prevents reflection of X-rays and/or vacuum ultraviolet rays, the reflective part and the non-reflective part (n1) are composed of a multilayer laminated film in which at least two types of substances having different optical constants are alternately laminated. That's what I did.

(Example) FIG. 1 is a schematic sectional view of an example of a reflective mask of the present invention. In the figure, 10 is a multilayer film m for soft X-rays, etc.
This is a reflective part made of a film.

As shown in the figure, this reflecting section 10 is formed on a non-reflective planar substrate 1 that absorbs soft X-rays and the like. 16 is a non-reflective part made of a multilayer laminated film against soft X-rays, etc.;
It is provided on the surface of the reflecting section 10 and forms a pattern of a predetermined shape.

The reflecting portion 10 is made of a first material 2°4.6. having different optical constants.
-... and second substance 3, 5, 7. -... are formed by laminating them alternately.

Thicknesses d, d of each material layer of the reflective section 10 shown in the figure
2.- is 10 Å or more, and even if the film thicknesses are alternately equal (d+ = d: + ==, d2 = d4 = -), all film thicknesses may be changed.

However, considering both the decrease in amplitude due to absorption of soft X-rays and vacuum ultraviolet rays in each layer, and the intensification of reflected light due to overlapping phases of reflected light at the interface of each layer, Preferably, the thickness is such that a high reflectance can be obtained. If the thickness of each layer is less than 10 layers, it is not preferable because a high reflectance cannot be obtained as a reflective part due to the effect of diffusion of the two substances at the interface. The reflectance increases as the number of layers increases, but
On the other hand, manufacturing difficulties arise. Therefore, the number of laminated layers is preferably 200 or less.

Moreover, the non-reflective part 16 is a reflective part 1F film for the reflective part 10, and the film thicknesses d, d2°, etc. of each layer are 1θ
d+
=d3=..., dz =d4=-), all JIS
! The structure may be configured by changing N.

As a reflective mask, the ratio of the intensity of soft X-rays etc. reflected by the reflective part 10 and the non-reflective part 16 is 2=1, preferably 10.
:It is better to have 1 or more. Therefore, although the number of layers of the antireflection film strongly depends on the wavelength range used, it is preferable to have two or more layers. For example, it is preferable to provide three or more layers for soft X-rays for around 100 people.

On the other hand, the film thickness per layer of anti-reflection film is 111
2 (from the conditions for movement, approximately λ/4 n(
λ is the wavelength and n is the refractive index), and when the number of layers is increased, the thickness of the non-reflective member becomes larger. the result,'
Except when irradiating soft X-rays etc. perpendicularly to a reflective mask,
A shadow may be caused by a non-reflective part on a reflective part. When a reflective mask is irradiated with soft X-rays at an incident angle of θ measured from a direction perpendicular to the reflective mask, the width of the reflective part is a, the total width of the non-reflective part is θ, and as a result, the reflective part The width of is effectively a
−2d tanθ. What is the width of the shadow relative to the reflective part? 7
3. It is preferably less than 1/Iθ, and as a result, if the angle of incidence cannot be changed, the width of the non-reflective member needs to be reduced. For example, when the width of the reflective portion is 0.2 μm, the thickness of the non-reflective portion must be 1900 nm or less than 600 Å at an incident angle of 10°.

Reflective masks are often used using powerful X-rays 12 (for example, from a light source using synchrotron radiation or the like), and a temperature increase in the mask due to absorption of irradiation energy becomes a problem. In particular, thermal expansion caused by temperature rise causes misalignment and distortion of patterns on the mask surface, which is an important problem when forming submicron-sized patterns.

For this reason, in a reflective mask using soft X-rays or the like, it is necessary to suppress the temperature rise of the reflective mask.

The reflective mask in this embodiment can use a bulk material for the substrate, and the mask itself can be cooled with water, so that the adverse effects of temperature rise can be significantly reduced. or,
By using materials with high thermal conductivity for the substrate and the multilayer laminated film, as will be described later, heat is effectively dissipated and temperature rise is prevented.

In addition, in this embodiment, a material with a small coefficient of linear expansion, as will be described later, is selected for the substrate and the multilayer laminated film to minimize the occurrence of distortion due to temperature rise.

Examples of substrate materials that satisfy the above conditions include ceramic silicon nitride, aluminum nitride, and silicon carbide. In particular, silicon carbide is a suitable material because it has extremely high thermal conductivity (100 w/m). Further, as one material of the multilayer stack 1112, transition metals such as tungsten, tacite, molybdenum, rhodium, and ruthenium, and their carbides, nitrides, silicides, borides, and oxides are suitable. The other material is silicon, beryllium,
Silicon oxides such as carbon, boron and their mutual compounds, such as silicon carbide, hexa-boron carbide, and their oxides and nitrides.

Silicon nitride or the like is suitable.

In particular, silicon carbide has a linear expansion coefficient of -1 to 4.5 x 10'', tungsten has a linear expansion coefficient of -1 to 4.5 It is a suitable material with a coefficient of -1 to 4.8 x 10-'.

In this example, materials with a linear expansion coefficient of I x 10-57 or less and a thermal conductivity of 2017 m- or more are used for the substrate, the reflective part, and the non-reflective part. preferable.

Next, a first embodiment of the method for manufacturing a reflective mask according to the present invention will be described with reference to FIG.

First, as shown in Fig. 3(A), the surface roughness of the substrate l is r.
The first layers 2.4, 6. - Molybdenum (Mo, coefficient of linear expansion 5.OX 10
−' to 1', thermal conductivity 139 w/m), second layer 3
,5,7. - Silicon (Si, coefficient of linear expansion 2.5 x 10-' -1, thermal conductivity 168w
/m), I X 10-'P a (Pascal)
After reaching an ultra-high vacuum of F, the argon pressure was increased to 5 x 1O
The first layer (Mo
), and the thickness of the second layer (Si) is 27 people each, :l
41 layers (21 Mo layers, 20 Si layers) were laminated in a LQ pattern to form the reflective section 10. Then, carbon was laminated as a protective film A on the reflective part 10.

In this case, the material selected is such that the first layer (Mo) has a small real part of the refractive index, and the second layer (Si) has a large real part of the refractive index.

Next, as shown in FIG. 3(B), a layer of PMMA (polymethyl methacrylate) as a resist is formed to a thickness of 0.5 μm on the surface of the reflective portion 10, and a 1.75 μm line & I did a space bashing. A patterned resist B made of this PMMA was formed.

On the patterned resist B made of this PMMA, Si,
71 people each with alternating Mo film thickness.

37 people, 31 people..., 36 people, 32 people, 36 people.

Thirty-three people sputter-deposited only 13 layers. The conditions for sputter deposition are the same as those for manufacturing the reflective section 10.

Next, the resist B was peeled off, and a multilayer film non-reflective portion 31 was formed on the reflective portion IO. (Figure 3 (C)).

The total thickness of the non-reflective portion 31 was 480 mm.

In order to confirm that the non-reflective part has the effect of an anti-reflection film on the reflective part, when performing sputter deposition in the production of the reflective mask described above (when producing the reflective part and when producing the non-reflective part), At the same time, a reference sample was set in the vapor deposition apparatus. Three reference samples were set when producing the reflective part, and one of the reference samples was set again when producing the non-reflective part.

This made it possible to measure the reflectance of the reflective part and the reflectance of a non-reflective part formed on the reflective part surface, and when the reflectance was measured at a wavelength of 130 people and an incident angle of 100, it was 52% for each. , a reflectance of 28% was obtained.

In order to confirm how much thickness is required when simply forming an absorber, Mo was deposited on the reflective part of the reference sample by 3,000 people and the reflectance was measured under the same conditions as the reflectance measurement described above. measurements were taken. As a result, a reflectance of 3.4% was obtained, and it was confirmed that just forming an absorber would require a considerably thick absorbing layer.

Next, a second embodiment of the method for manufacturing a reflective mask according to the present invention will be described. The substrate 1 is similar to the first embodiment shown in FIG.
A reflective section 10 was provided thereon, and a pattern of a predetermined shape was further formed thereon using a resist made of PMMA. Next, after reaching a high vacuum of less than I
Q-' -1, thermal conductivity Plow/+) Tungsten W (linear expansion coefficient 5XlO-' -1, thermal conductivity 178 stomach/
IIK) alternately, and membrane J'J for 73 people each.

A non-reflective portion consisting of 6 layers was formed with 108, 29, 38, 30, and 40 layers. Next, PMMA
The resist made of the multilayer film was peeled off, and a non-reflective part made of the multilayer film was formed on the reflective part surface of the multilayer film. The total thickness of the non-reflective part is 318 mm.

In this example as well, a reference sample was prepared in the same manner as in the first example, and the antireflection effect of the non-reflective portion was confirmed. The reflecting section was manufactured at the same time as the first example, and a reflectance of 52% was obtained at a wavelength of 130 and an incident angle of 10 degrees. The reflectance of the non-reflective portion formed on the reflective portion was 3.2%.

Form W to a thickness of 720 mm on the reflective part surface of the reference sample,
The absorber has a reflectance of 4.7%, and an absorber that has the same effect as the non-reflective part of the multilayer film needs to be at least twice as thick as the J7 thickness of the non-reflective part of the multilayer film. It was confirmed that

In each of the above embodiments, the protective film provided on the upper surface of the reflective section is preferably carbon with a thickness of 100 Å or less, but it does not need to be provided.

In this embodiment, the case where the multilayer laminated reflective section is constructed by laminating two materials alternately is shown, but it may be constructed by laminating three or more materials alternately.

In addition, although the sputtering method was used to form the multilayer film, it is not limited to this, and various other methods for forming thin films such as EB evaporation, resistance heating, CVO, and reactive sputtering may be used. can.

In addition, although a Si single crystal plate was used as the substrate, it is not limited to this, but it is also possible to use a substrate made of glass, fused silica, silicon carbide, etc., which has been polished so that its surface is seven times smoother than the wavelength used. It's good to have.

(Effects of the Invention) According to the present invention, by forming a pattern of a predetermined shape on a substrate surface by a reflective part and a non-reflective part made of a multilayer film having the above-mentioned structure, it is possible to It is possible to obtain a reflective mask for lithography using soft X-rays or the like, which has a simple configuration and allows incidence of the soft X-rays. In addition, by selecting a material with a predetermined coefficient of linear expansion and thermal conductivity for the multilayer film, it is possible to achieve a reflective mask that is extremely thermally stable and has low distortion. Since the thickness can be made thinner, soft x, S! The permissible range of the irradiation angle of a and vacuum ultraviolet rays is widened, and a greater degree of freedom can be given to the optical system of the exposure apparatus.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an embodiment of a reflective mask of the present invention, FIG. 2 is an explanatory diagram of a reflective mask using an absorber as a non-reflective part, and FIG. 3 is a reflective mask of the present invention. FIG. 2 is an explanatory diagram of a first example showing a method for manufacturing a mask. In the figure, 1.25 is the substrate, 10, 24.32 is the reflective part of the multilayer film, 16.31 is the non-reflective part of the multilayer film, A is the protective film, and B
21 is a resist, 2.4 is a first substance, and 3. is a resist.
5 is the second substance. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) A reflective part that reflects soft X-rays and/or vacuum ultraviolet rays is provided on a substrate surface that is non-reflective to soft X-rays and/or vacuum ultraviolet rays, and furthermore, a reflective part that reflects soft A reflective type characterized in that the reflective part and the non-reflective part are formed of a multilayer laminated film in which at least two types of substances having different optical constants are alternately laminated when providing a pattern consisting of a non-reflective part to prevent reflection of the reflective part. mask.