JPH02123730A - Radiation exposure mask and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a mask for radiation exposure having low stress and a high-density radiation absorber pattern by using alloy comprising two kinds of metal elements which are selected among high-density, high-melting-point metal elements such as W and RE, and constituting an alloy film. CONSTITUTION:A substrate is heated, and a W-Re alloy film 1a is deposited at a pressure of 4 Pa. Then an SiO2 film (upper layer film) 5a is deposited by a sputtering method. An electron beam resist film 4a is applied, and a desired resist pattern 4 is drawn. With the pattern as a mask, the SiO2 film 5a undergoes selective dry etching by using CHF3 reacting gas. Thus an SiO2 pattern 5 is formed. With the pattern 5 as a mask, dry etching is performed under the specified conditions by using SF6 gas, and a radiation absorber pattern 1 comprising W-Re alloy is formed. Thereafter, the SiO2 pattern 5 is removed, and a mask for radiation exposure is formed. Thus, the mask for radiation exposure having low stress and the high-density radiation absorber pattern can be obtained with good productivity at a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radiation exposure mask used for transferring fine patterns in the manufacture of semiconductor integrated circuits, and a method of manufacturing the same.

[Conventional technology]

2. Description of the Related Art Au, W, or W-Ti alloy film patterns have been used as X-ray absorber patterns used in X-ray exposure masks used in the manufacture of conventional semiconductor integrated circuits. Since Au has a large X-ray absorption coefficient and can provide a plating material with low stress, it is suitable for producing a low-distortion X-ray exposure mask. However, since the plating process is a wet process, many defects occur in the formed pattern, and depending on the area of the pattern, it may be necessary to change the plating current, so setting the best process conditions to maintain low stress at all times. was extremely difficult. W has the advantage that it has a large X-ray absorption coefficient and that a steep pattern cross-sectional shape can be obtained by reactive etching using CF or the like. However, it is difficult to form a film with low stress, and xIv! This causes positional distortion of the exposure mask.
There was a drawback that it was not possible to transfer fine patterns with high precision. - Mask patterns for X-ray exposure made of W-Ti alloy can be etched using a reactive ion etching method, as proposed in JP-A No. 63-51632. It has the advantage of being able to be microfabricated by microfabrication and improving adhesion to materials such as SiN and Sin. Also, Niss B.I.
E., Proceedinges, No. 923 (1988)
, pages 2 to 8 (SPIE Proceedings
s 923 (1988), pp 2-8), it is possible to make low stress W-Ti alloy X-ray exposure masks.

However, since Ti is a light metal element, the density of one alloy will not be higher than that of W alone, and a large amount of T
The W--Ti alloy containing i has a drawback of having a small X-ray absorption coefficient.

[Problem to be solved by the invention]

'' As shown in the same paragraph, conventional technology has high density and large X-ray absorption coefficient, low stress and excellent workability,
Moreover, it has not been possible to obtain an X-ray absorber material that satisfies all the conditions of being less likely to cause pattern defects.

The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, and to provide a radiation exposure method having a radiation absorber pattern that has a large radiation absorption coefficient, low stress, good workability, and is capable of transferring fine patterns with high precision. An object of the present invention is to provide a mask and a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above object of the present invention, an alloy consisting of at least two kinds of metal elements selected from among high-density, high-melting point metal elements such as W, Ta, Re, Os, and Ir is used as a radiation absorber material. and the constituent elements of the alloy are a combination of elements in which one element has a resting cubic lattice structure and the other element has a face-centered cubic lattice structure or a hexagonal close-packed lattice structure. The metal element is made to be able to enter the space of the crystal lattice of other metal elements to form a high-density, low-stress alloy film.

The present invention provides a radiation exposure mask in which a predetermined radiation absorber pattern is formed on a mask substrate. , Ir, one of the constituent elements of the alloy is an element with a body-centered cubic structure, and the other element has a face-centered cubic structure or a hexagonal close-packed structure. The present invention is a radiation exposure mask having a low-stress, high-density radiation absorber pattern in which, as a combination of elements, the elements constituting the alloy enter into the crystal lattice spaces of other elements.

In the radiation exposure mask of the present invention, it is preferable that the materials constituting the radiation absorber pattern are an alloy in which one of the materials is W or Ta and the other is Re, Os, or Ir.

In the radiation exposure mask of the present invention, the material constituting the radiation absorber pattern is made of an alloy of W and Re, and the alloy of W and Re has a Re content of 5 to 95% by weight. It is more preferable to fall within the range of .

Furthermore, in the radiation exposure mask of the present invention, the material constituting the radiation absorber pattern is made of an alloy of Ta and Ir, and the alloy of Ta and Ir has an Ir content of 80% or less by weight. It is more preferable that

The method for manufacturing a radiation exposure mask having a radiation absorber pattern according to the present invention includes a method for manufacturing a radiation exposure mask having a radiation absorber pattern.
a step of sequentially laminating an alloy film made of at least two elements selected from , s, and Ir, and an upper layer thereof, and applying an electron beam resist film thereon; A step of drawing a desired pattern on the film using an electron beam, and then developing it to form a resist pattern, and using the resist pattern as a mask, selectively etching the upper layer film to form an upper layer film pattern. and selectively etching the alloy film with a reactive gas using the upper layer film pattern as a mask to form a desired radiation absorber pattern made of the alloy film. A radiation exposure mask having a low-stress and high-density radiation absorber pattern according to the present invention can be obtained.

In the method for manufacturing a radiation exposure mask of the present invention, W-Re, Ta-
The upper layer film formed on top of the alloy film such as Ir is made of
, 5i02 or SiN, 5L3
Preferably, a silicon nitride film such as N4 is used.

Furthermore, in the method for manufacturing a radiation exposure mask of the present invention, it is preferable to use sulfur hexafluoride (sFs) as a reactive gas for selectively etching a low-stress, high-density alloy film.

[For production]

The materials used as radiation absorber pattern materials are all made of metal elements with large atomic numbers,
The X-ray absorption coefficient is also large, and alloys made of these metal elements also have a large X-ray absorption coefficient. By forming an alloy, even if it is difficult to reduce stress with a single metal element, one of the metals has a body-centered cubic lattice structure.
By combining metal elements with the other one having a face-centered cubic lattice or hexagonal close-packed lattice structure, the interlattice distance of the crystal can be changed, and a low-stress alloy film can be obtained as a radiation absorber pattern material. can. Also, by forming an alloy film having the above structure.

Microfabrication by reactive ion etching or the like becomes easy, and it becomes possible to manufacture radiation exposure masks with low stress and high density radiation absorber patterns with high productivity and high yield.

(Example) An example of the present invention will be described below in more detail based on the drawings.

FIG. 1 is a schematic diagram showing an example of the cross-sectional structure of a radiation exposure mask manufactured by the manufacturing method of the present invention. FIGS. 2(a) to 2(e) are process diagrams showing the manufacturing process of the radiation exposure mask shown in FIG. 1 above.

First, LPGVD (Low Pressure Chemical Vapor Deposition) is applied onto a Si wafer.
BN by apor Deposition) method
A C film was formed. The reaction gas used was monomethylamine, diborane diluted with 5% by volume hydrogen, and the pressure was 666.61 Pa, 75
A film was formed to a thickness of 2 μm at 0°C. B on the back side of the Si wafer
The central part of the NC film was removed by dry etching with CF according to the window shape, and using this as a mask, the Si wafer was wet etched from the back side with a mixture of hydrofluoric acid: nitric acid: acetic acid = 1:4:1. A BNC mask membrane 2 was formed.

Using an RF sputtering device, W with a Re content of 30 wt% was
- Using a Re mixed target, the substrate was heated to 400°C, and a W-Re alloy film 1a was formed to a thickness of 1 μm under a pressure of 4 Pa.
was deposited. Next, a SiO□ film (upper layer film) 5a is deposited to a thickness of 0.1 μm by sputtering, and an electron beam resist film 4
A was applied [Figure 2 (a)].

Next, a desired resist pattern 4 is drawn with an electron beam resist film 4a and developed [FIG. 2(b)].

Using this resist pattern 4 as a mask, the 5in2 film 5a was selectively dry etched using CHF and a reactive gas to form a Sio2 pattern 5 [FIG. 2(C)].

Furthermore, using this 5in2 pattern 5 as a mask, SF,
Using gas, 26.664 Pa, 0.35W/
, :n to form a radiation absorber pattern 1 made of W-Re alloy, and then Si
The O□ pattern 5 was removed to produce a mask for radiation exposure [FIGS. 2(d) and (e)].

In addition to BNC, the radiation exposure mask may be made using 5iC1SiN, BN, or Si as the membrane. Furthermore, if the selectivity between the membrane and the W-Re alloy film cannot be ensured, a stopper such as Sio2 may be appropriately formed between the membrane and the W-Re alloy film.

In addition, wet etching on the back surface of the Si wafer does not cause positional distortion before electron beam lithography.

Therefore, immediately after the W-Re alloy film is deposited or
It may be done immediately after the O2 film is deposited.

Figure 3 shows the internal stress (N/rrr) and Re content (wt%) of the W-Re alloy thin film produced by RF sputtering.
shows the relationship between The relationship between the W-Re content and the internal stress was shown by changing the substrate temperature at 400° C., changing the Ar gas pressure, and changing the Re occupation area of the target.

When only W is targeted, the internal stress has a strong compressive stress. Also, when Re is used alone, it has compressive stress.

When Re and W are mixed, stress can be significantly reduced. As is clear from Figure 3, the Re content was increased to 5
When the range is from t% to 95υt%, the absolute value of stress can be almost 0 (2×10'N/i or less),
Positional distortion of the radiation exposure mask can be significantly reduced. Therefore, it can be seen that it is suitable to use a W-Re alloy film with low stress, that is, a W-Re alloy film containing 5 to 95 wt% Re, for the radiation exposure mask.

Figure 4 shows the density of the W-Re alloy film when the Re content is changed at a substrate temperature of 400°C and an Ar gas pressure of 1.33°C.
The case where the film was formed under the conditions of 3 Pa to lo and 666 Pa is shown. When the Ar gas pressure is high, W has a bulk density of 19.3
g/cnf. However, when Re is included, no decrease in density is observed even under high gas pressure, making it extremely suitable as an X-ray absorber material.

Next, using Ta and Ir as high-melting point, high-density metal materials, Ta-Ir
Internal stress (N/rrF) and Ir when forming an alloy film
The relationship between content (wt%) is shown in FIG. When only Ta is targeted, the internal stress of the Ta film changes greatly from strong compressive stress to tensile stress as the Kr gas pressure increases.

When Ir was used as the target, the Ir film had compressive stress, and when the film was formed using a mixed target of Ta and Ir, the stress of the Ta-Ir alloy film could be significantly reduced. As is clear from Figure 5, the Ir content was 0.11°C.
% to 80wt%, the absolute value of stress becomes approximately O(
2×10′N/rrr or less), and the positional distortion of the radiation exposure mask can be reduced.

Figure 6 shows Ta-
Regarding the density (g/e11?) of the Ir alloy film, room temperature, krypton (Kr) gas pressure 1.333 Pa to 10.666
When the sKr gas pressure shown for the case of the film formation condition of Pa is low, the density of the Ta-Ir alloy film is the density of the bulk (Ta
= 16.6 g/cd, Ir = 22.5 g/al). When Kr gas pressure is high, Ta -I
Although the density of the r-alloy film decreases, by making it an alloy film of Ta and Ir, the density of the Ta-Ir alloy film does not decrease much even under high Kr gas pressure, making it suitable as an X-ray absorber material. This shows that it is extremely suitable.

In addition to the combination of W-Re and Ta-Ir alloy films, the combination of W-Os, W-Ir, Ta-Re, and Ta-Os alloy films is similar to the above example. It has been confirmed that stress can be reduced, and as a high-density material, it can be used very suitably as an absorber material for radiation exposure masks.

【Effect of the invention〕

As explained above in detail, W is the radiation absorbing material of the present invention as a mask for radiation exposure.

An alloy consisting of at least two metal elements selected from among heavy metal elements with high density and large radiation absorption coefficient, such as Ta, Re, Os, and Ir, is used, and one of the metal elements constituting the alloy is a body. Since the metal element has a centered cubic lattice structure and the other has a face-centered cubic lattice or hexagonal close-packed lattice structure, atoms can enter into other crystal lattice spaces, reducing the stress of the formed alloy film by 2×10
'N10f or less, which has an excellent effect of being able to reduce the value to a value close to 0.
When used alone, only a low-density W film can be formed at high film-forming gas pressures, but by mixing Re, it has the effect of preventing oxidation and maintains the high density of the alloy film.
Moreover, it has become possible to produce a W-Re alloy film suitable for low-stress radiation exposure masks.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the cross-sectional structure of a radiation exposure mask exemplified in an example of the present invention, and FIG. 2 (a) to (,)
3 is a process diagram showing the manufacturing process of the radiation exposure mask produced in the example of the present invention, and FIG. 3 is a graph showing the relationship between the Re content and internal stress of the W-Re alloy film produced in the example, Figure 4 is a graph showing the relationship between Re content and density of the W-Ra alloy film produced in this example, and Figure 5 is a graph showing the relationship between the Ir content and internal stress of the Ta-Ir alloy film produced in this example. Graph showing the relationship between
The figure shows the Ir of the Ta-Ir alloy film produced in this example.
It is a graph showing the relationship between content rate and density. 1...Radiation absorber pattern 1 made of W-Re alloy
a...W-Re alloy film 2...BNC mask membrane 3...Si support frame 4...Resist pattern 4a...Electron beam resist film 5-S i O2 pa! i-:/5 a-S
In, film Figure 2 Figure W-Re, total R1f4Fe content 'r tW礪J Figure 3 Figure 4 Figure 7-1-1r A'Af41. Wtz Figure 5

Claims (1)

[Claims] 1. In a radiation exposure mask in which a predetermined radiation absorber pattern is formed on a mask substrate, the material constituting the radiation absorber pattern is W, which is a high-density, high-melting-point metal element; It is composed of an alloy containing at least two elements selected from Ta, Re, Os, and Ir, and one of the constituent elements of the alloy has a body-centered cubic structure, and the other element has a face-centered cubic structure. As a combination structure of elements having a structure or a hexagonal close-packed structure, the elements constituting the alloy have a low-stress, high-density radiation absorber pattern with a structure in which the elements constituting each other enter the space of the crystal lattice of other elements. Features of radiation exposure mask. 2. In the radiation exposure mask described in claim 1, the material constituting the radiation absorber pattern is an alloy in which one of the materials is W or Ta element and the other is Re, Os, or Ir element. A radiation exposure mask featuring: 3. The radiation exposure mask according to claim 1 or 2, wherein the material forming the radiation absorber pattern is made of an alloy of W and Re. 4. In the radiation exposure mask according to claim 3, the alloy of W and Re has a Re content of % by weight,
A mask for radiation exposure, characterized in that the radiation exposure is in the range of 5 to 95%. 5. A radiation exposure mask according to claim 1 or 2, wherein the material forming the radiation absorber pattern is made of an alloy of Ta and Ir. 6. The radiation exposure mask according to claim 5, wherein the Ta and Ir alloy has an Ir content of 80% by weight or less. 7. On a mask substrate, an alloy film made of at least two elements selected from W, Ta, Re, Os, and Ir and an upper layer thereof are laminated in sequence, and an electron beam resist is applied thereon. a step of applying a film, and drawing the electron beam resist film into a desired pattern with an electron beam;
Thereafter, a step of performing a development treatment to form a resist pattern, a step of selectively etching the upper layer film using the resist pattern as a mask to form an upper layer film pattern, and using the upper layer film pattern as a mask, A method for manufacturing a mask for radiation exposure, comprising at least the step of selectively etching the alloy film with a reactive gas to form a desired radiation absorber pattern made of the alloy film. 8. In the method for manufacturing a radiation exposure mask according to claim 7, the alloy film forming the radiation absorber pattern is a W-Re alloy film or a Ta-Ir alloy film, and the upper layer film is oxidized. A method for manufacturing a radiation exposure mask, characterized in that it is a silicon film or a silicon nitride film. 9. The method for manufacturing a radiation exposure mask according to claim 7, wherein the reactive gas that selectively etches the alloy film is sulfur hexafluoride (SF_6). manufacturing method.