JPH01200621A - Mask structure for x-ray lithography - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a mask structure for X-ray lithography.

[Conventional technology] X-ray lithography uses high transmittance (low absorption number) unique to X-rays.
, short wavelength, etc., it has many advantages over conventional lithography using visible light or ultraviolet light, and is attracting attention as an effective means of submicron lithography. However, the power of the x, vi source shortage,
Productivity is low due to low sensitivity of the resist, difficulty in alignment, difficulty in selecting mask materials and processing methods, etc.
The high cost has drawbacks, and practical application has been delayed.

Among these, taking up masks for X-ray lithography, in visible light and ultraviolet light lithography, glass plates and quartz plates have been used as mask material holders (i.e., light transmitting bodies); In lithography, the wavelengths of light that can be used range from 1 to 200, and conventional glass plates and quartz plates have large absorption in the X-ray wavelength range and have to be thick, 1 to 2 mm. Since they are not transparent, they do not allow enough X-rays to pass through them, so they are unsuitable as materials for mask material holders for X-ray lithography.

Since X-ray transmittance generally depends on the density of a substance, low-density inorganic and organic materials are being considered as materials for mask material holders for X-ray lithography. Examples of such materials include beryllium (Be) and titanium (T).
i) Inorganic materials such as silicon (Si), boron (B) alone and compounds thereof, and organic materials such as polyimide, polyamide, polyester, parylene, and the like.

In order to actually use these substances as materials for mask material holders for X-ray lithography, it is necessary to make them into thin films in order to maximize the amount of X-ray transmission. In this case, it is required to form the film with a thickness of several tens of microseconds or less. For this reason, for example, when forming a mask material holding film consisting of an inorganic thin film or a composite film thereof, a thin film of silicon nitride, silicon oxide, boron nitride, silicon carbide, etc. is formed by vapor deposition on a silicon wafer with excellent flatness. A method has been proposed in which the silicon wafer is then removed by etching.

In addition, as the mask material for X-ray lithography (i.e., X-ray absorber) held on the above-mentioned holding R4 film,
Thin films of dense materials such as gold, platinum, tungsten, copper, nickel and compounds containing these are commonly used.

In particular, a thin film having a thickness of 0.5 to 1 μm is preferably used.

Such a mask material is produced by, for example, uniformly forming a thin film of the high-density material on the X-ray transparent film, applying a resist, and drawing a desired pattern on the resist using an electron beam, light, etc. Thereafter, a desired pattern is created using means such as etching.

[Problems to be Solved by the Invention] As described above, in conventional X-ray lithography, the X-ray transmittance, visible and near-infrared transmittance of the mask material holding thin film is low, and sufficient X-ray transmittance and visible In order to obtain the amount of near-infrared light transmitted, the mask holding film needs to be several microns or less. However, it is not always easy to do so, and the yield is not good. There is also a problem with strength.

In addition, the physical properties change due to minute differences in film thickness, making it unsuitable for manufacturing with good reproducibility.

In addition, in recent years SOR light has attracted attention as an X-ray source, and compared to the characteristic X-rays generated from conventional electron impact X-ray sources, it uses a wider range of wavelengths and has greater power.
X-ray transmittance over a wide range of wavelengths, thermal stability, and X-ray resistance of mask material holders for line lithography have become major issues. - The present invention has high X-ray transmittance over a wide range of X-ray wavelengths (1 to 10 people), and exhibits sufficient light transmittance even at a thicker thickness than conventional products, making it suitable for improving strength and yield. An object of the present invention is to provide a mask structure for X-ray lithography equipped with a mask holder.

Another object of the present invention is to provide an X-ray mask material holder that satisfies visible light transmittance and has good thermal dimensional stability and X-ray resistance.
An object of the present invention is to provide a mask structure for line lithography.

[Means for Solving the Problems] The above object is to provide a mask material holding thin film consisting of a single layer film containing aluminum, boron, nitrogen and oxygen as main components or a laminated film containing at least the film, and the mask material holding thin film. an annular holding substrate for holding a peripheral portion of the X-ray lithography mask structure.

Regarding Al, N, B, 0 of a film mainly composed of aluminum, boron, nitrogen and oxygen, (8lN: 8j2
03=1:1~5): (BN:B203)=1
:1-5)=1:1-10 (molar ratio) is preferable.

Note 1. The annular holding substrate is preferably made mainly of silicon, pyrex glass, quartz, invar, or stainless steel.

[Effect] For X-rays shorter than the absorption edge of 11 (1 to 8.34),
Boron (B) has good transmittance and long wavelength (8,34~I
Since the transmittance of Aj is good for X-rays (O person), the AA-B-N-0 film exhibits high transmittance for X-ray sources with a wide wavelength range, such as SOR. Therefore, the Aj-B-N-0 film exhibits a transmittance of 50% or more at two scale thicknesses. In order to show the same transmittance, many inorganic materials (silicon nitride films, etc.) need to be as thin as about 1 liter.
The film is easy to manufacture and can improve the yield of mask structures for X-ray lithography.

Since the 11-B-N-0 film has a high visible light content of 98% or more when it has a thickness of 2 μm, alignment using visible light is easy.

^7-The thermal expansion coefficient of B-N-0 film is 3 to 4 x 10-6/'
Since C and generally the printing are approximately the same values as those of a silicon wafer which is preferably used as a substrate, it is possible to print both with extremely high precision.

1l-B-N-0 film has a thermal conductivity of 1-2 Wcm'k
-' (1 silicon nitride is 0.17~0.3wcr
n-'k-'), it is possible to prevent temperature rise due to X-ray irradiation.

In addition, normally, when forming a thin film, 02 is mixed in, which may cause a large change in the physical properties of the formed film, but by intentionally controlling and forming a film containing 0°, , a stable film can be obtained.

[Example] Example 1 Using sputtering on the back surface of the silicon wafer 11, a 2μ
A thick silicon oxide (SiO□) film 12 was formed (first
Figure (a)). This wafer 11 is set in a thermionic impact type ion blating device, the evaporation source is aluminum (Al) and boron oxide (B203), and the gas is argon (Ar):nitrogen (N2) = 3: 1, the gas pressure is 3xlO-'Torr, and the discharge power is 40
W, acceleration voltage 600V, substrate temperature 80℃, to 1-B
-N-0 film 13 was formed (FIG. 2(b)).

Next, in order to leave SiO□Ili 12 in a ring shape,
A layer of avinisine wax (manufactured by Shell Chemical Co., Ltd.) was formed (Figure (c)), and this was used as the protective film 14, and the central part of the 5in2 film 12 was removed using a mixed solution of ammonium fluoride and hydrofluoric acid. ((d) in the same figure). Thereafter, the abinisin wax was removed with xylene (FIG. 1(C)).

After that, silicon wafer 11 was coated with potassium hydroxide aqueous solution.
8j-B-N-o IIQ
Both sides of 13 were exposed (FIG. 1(f)).

Finally, a gold (Au) mask material 15 is formed using EB drawing and electroforming, and Aj-
An X-ray mask using the B-N-0 film 13 as a transmission film was manufactured (FIG. 1(g)).

Example 2 A silicon nitride film (SiNx) 12 having a thickness of two scales was formed on the back surface of a silicon wafer 11 using plasma CVD.

Next, this wafer was set in an MOCVD apparatus, and trimethylaluminum was applied to the wafer while heating it to 500° C. at 50 sccM. 1 diborane ([12+16)
5 using 12 carrier gases! i C CM , flow 10 SCCM of nitrogen oxide (N20) gas, l-B-N
A -0 film 13 was formed (FIG. 2(b)).

Next, apply a negative resist (OMR-83, manufactured by Tokyo Ohka Co., Ltd.) in a ring shape (see figure (C)), and apply it to the protective film 1.
4, the center of SiNx15i 1 2 was removed using a mixed solution of ammonium fluoride and hydrofluoric acid (see the same figure).
d)) The resist was removed using a special stripping SFI ((C) in the same figure).

Next, the silicon wafer 11 was back-etched with hydrofluoric nitric acid (FIG. 4(f)).

On top of that, add 0. 77u, Sin2 is 0.
3. The resist pattern was deposited in the order of at, and was created by EB drawing. The resist pattern was transferred to Sin2 by dry etching with (:F4+82 gas) and transferred to Ta by etching with CBrF3 gas, thereby producing a mask material 15 of Ta. 8t-B-N-
An X-ray mask using 0 11% 1 3 as a transparent film was manufactured.

Example 3 Using sputtering on the back surface of silicon wafer 11,
A thick silicon oxide (Sin2) film 12 was formed (FIG. 2(a)).

Next, this wafer 11 is sputtered using a high-frequency sputtering device using an aluminum boride (IB) target, argon (Ar):nitrogen (N2):oxygen (0,) ==3:
A two-layer thick AA-B-N-0 film 13 was formed at I: 0.5, gas pressure of 5×10 −3 Torr, and discharge power of 200 W (FIG. 2(b)).

Next, apply a positive resist (AZ-1370: manufactured by Hoechst Co., Ltd.) in a ring shape (Figure (C)), and apply it to the protective film 14.
((d) in the same figure)
The resist was removed using a special stripping solution (see the same figure).
e)).

Next, the center portion of the silicon wafer 11 was etched using a potassium hydroxide (KOH) aqueous solution (FIG. 1(f)).

On top of that, 100 Cr and 7000 8U were deposited in order, and mask material 15 was formed by direct drawing using a focused ion beam device (FIB), and AI--B-N-o11q
An X-ray mask using t3 as a transmission film was manufactured.

Example 4 A two-layer thick silicon nitride (SiNx) film 12 was formed on the back surface of a silicon wafer 11 using plasma CVD (FIG. 2(a)).

Next, in the same manner as in Example 2, 2
A μ-faced ^j-B-N-0 film 13 was deposited (see figure (b)
).

Next, a mask material 15 was formed ((C) in the same figure).

Although any of the methods of Examples 1 to 3 may be used for this purpose, the method of Example 1 was actually used.

Next, apply a positive resist (OFPR-800 manufactured by Tokyo Ohka Co., Ltd.) in a ring shape (see figure (d)), and apply it to the protective film 1.
4, the center of the SiNx film 12 is removed using a mixed solution of ammonium fluoride and hydrofluoric acid (FIG. 4(e)).
The resist was removed using a special stripping solution (see figure (f)
)).

Finally, the silicon wafer 11 is back-etched with ethylenediamine and pyrocatechol, and An-B
- An X-ray mask using the N-0 film 13 as a transparent film was created (
Figure (g)).

[Effects of the Invention] As explained in detail above, in the present invention, the 1-B-N-0 film used as the X-ray transmitting film transmits X-rays in a wide wavelength range.
Because it has high radiation transmittance and visible light transmittance, low coefficient of thermal expansion, and high thermal conductivity, the X-ray transmitting film can be made thicker than conventional films with the same transmittance, which improves reproducibility. Easy to manufacture, high yield, and improved strength.
Alignment using visible light is easy, ・Thermal dimensional stability is improved, ・Physical properties are stabilized by adding 02, ・Suitable for use in X-ray lithography using SOR light as a light source, which uses a wide range of wavelengths. .

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams each showing the manufacturing process of the mask structure for X-ray lithography of the present invention. 11: Silicon wafer 12: Film 13 made of Sin□ or SiNx:
AA-B-N-0 film 14: Protective film 15: Mask material patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1) A mask material holding thin film consisting of a single layer film containing aluminum, boron, nitrogen and oxygen as main components or a laminated film containing at least the film, and a peripheral portion of the mask material holding thin film. 1. A mask structure for X-ray lithography, comprising an annular holding substrate for use in X-ray lithography. 2) The mask structure for X-ray lithography according to claim 1, further comprising a mask material applied in the form of a thin film over one surface of the mask material holding thin film. 3) Claim 1 further comprising a mask material applied in a thin film pattern to the mask material holding thin film.
A mask structure for X-ray lithography as described in 1.