JPH04151818A - Method for manufacturing a mask structure for 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 (Field of Industrial Application) The present invention relates to a lithography mask structure used when printing fine patterns of large-scale integrated circuits (LSI), micromachines, etc. onto wafers, etc. by X-ray exposure. Regarding the manufacturing method.

(Prior art and its problems) Large-scale integrated circuits represented by DRAM are now 4MDRA
M is in the mass production period, and from 16M DRAM to 64M
Technology is rapidly progressing towards DRAM. Along with this, the minimum line width required for devices has also been reduced from half a micron to a quarter micron.

These semiconductor devices are transferred from a mask to a semiconductor substrate using near-ultraviolet light or far-ultraviolet light, but the line width of devices that can be processed using these wavelengths of light is approaching its limit. Further, the depth of focus inevitably decreases due to miniaturization. Therefore, a lithography technique using x8I, which has an even shorter wavelength, has been devised, and there are great expectations that this will solve the above problems at the same time.

The mask structure used for such X-ray exposure has a structure in which a fine pattern of an X-ray absorber is further formed on an X-ray transparent film formed on a suitable support frame. Furthermore, heavy metals, particularly Au, W, Ta, etc., are used as the X-ray absorber material.

Furthermore, the X-ray absorber pattern is supported and fixed.
A silicon compound material such as SiN or SiC is used for the light-transmitting film.

In addition, methods for forming the X-ray absorber pattern include a plating method for a diagonal pattern using a resist, a dry etching method in which a thin film of a heavy metal absorber is patterned by a dry process such as reactive ion etching, or a suitable method. There are web 1 to etching methods in which patterning is performed by a wet process using an etching solution.

By the way, regarding the shape of this X-ray absorber, when considering Fournel diffraction of X-rays incident on the mask, it is better to have a cross-sectional shape that is not perpendicular to the mask substrate surface.
A desirable method for pattern transfer to resist has been proposed (Japanese Patent Laid-Open No. 2-52416). Also, even more X on the mask
Considering the reduction in the resolution of the resist due to reflection on the side walls of the absorber pattern when a line is incident, it is desirable that the cross-sectional shape of the absorber pattern is a trapezoid having a long dimension on the substrate surface.

However, when attempting to create such an X-ray absorber pattern with an arbitrary cross-sectional shape using the dry etching method described above under the same conditions, it is difficult to set the etching liquid conditions for the angle of the side wall of the absorber pattern. There is glume.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for manufacturing a lithography mask structure in which the cross-sectional sidewall of an X-ray absorber can be controlled at an arbitrary angle.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a method for manufacturing an X-ray mask structure including a step of forming an X-ray absorber in a desired pattern on an X-ray transparent film, in which the X-ray absorber pattern is formed by a dry etching method. This is a method for manufacturing a lithography mask structure characterized by alternately performing anisotropic etching and isotropic etching.

(Function) As a result of intensive research, the present inventors found that
When forming a line absorber pattern using a dry etching method, the dry etching method is divided into anisotropic etching conditions in which the shape of the absorber pattern is perpendicular to the substrate surface and isotropic etching conditions in which the shape of the absorber pattern is trapezoidal or triangular. This book was developed based on the discovery that the angle of the sidewall of the absorber pattern relative to the substrate surface could be advantageously controlled by setting two dry etching conditions and alternating these conditions at a certain time interval. This led to the invention.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The lithography mask structure formed by the method of the present invention basically consists of a mask support frame made of a silicon wafer, an X-ray transparent film on the support frame, and an X-ray absorbing film formed on the X-ray transparent film. Consists of body patterns. Furthermore, in addition to these, a protective film for an X-ray absorber, a conductive film, etc. may also be used.

Examples of the material for the X-ray transparent film include Si, 5in2.
Known materials such as inorganic films such as SiC, SiN, BN, and BNC, and radiation-resistant organic films such as polyimide can be used. In addition, any material that can be used as an X-ray transparent film can be used. In addition, as a method for forming the X-ray transparent film, various sputtering methods, chemical vapor deposition methods, etc. are used, and 1 to 1 portion of the above TA material is deposited on the mask support frame.
A film is formed to a thickness of 0ILm to form an X-ray transparent film.

) Examples of materials for the J9 absorber pattern include Ta,
Known materials such as Ta<B, W, WNX, W T 1, etc. can be used, and in the method of the present invention, a film made of such materials is patterned by a dry etching method.

In the present invention, when patterning an X-ray absorber film using this dry etching method, the sidewall angle of the cross-sectional shape of the absorber pattern is adjusted relative to the substrate surface by alternately performing tri-etching under two different conditions. It is characterized by being able to be controlled arbitrarily.

Methods for controlling the sidewall angle of the cross-sectional shape of the X-ray absorber pattern with respect to the substrate surface include changing the etching anisotropy by changing the substrate temperature, and forming a film on the pattern sidewall during etching. There is a method in which gas species and non-film forming gas species are alternately introduced into the etching chamber. When comparing both methods relatively,
The latter method is more suitable when considering actual control, and this method was also used in the present invention.

In the latter method, CF4. CCf
14. Examples include halogenated hydrocarbons such as CBrF3 and hydrocarbon gases such as CH4.

Conversely, a halogenated gas that does not contain carbon, such as SF, NF3, etc., can be used as a gas that does not cause a film to adhere to the side walls of the pattern during etching.

By employing the above method, the X-ray absorber pattern on the X-ray transparent film becomes trapezoidal as shown in the first diagram. In the present invention, the angle of the side wall of the trapezoid with respect to the underlying substrate is 8.
It is preferable to set it as the range of 0-87 degrees.

Note that other configurations used in the method of the present invention, such as back etching of the underlying substrate and adhesion of the reinforcing agent, may be conventionally known configurations (but are not particularly limited).

(Example) Next, the present invention will be described in more detail with reference to Examples. It goes without saying that the present invention is not limited to the examples.

Example 1 A SiN film with a thickness of 21 Lm was formed by chemical vapor deposition on a mask support frame made of a silicon wafer, and this was used as an experimental substrate.

Next, a film of W as an X-ray absorber was formed on this substrate by sputtering to a thickness of 0.81 zm. Furthermore, on top of this
As a mask material during etching, a Cr film was formed to a thickness of 300 nm by electron beam evaporation.

Next, 0.5% of PMMA, which is an electron beam resist, is applied on top of it.
μm μm bispin coating 0.257 person m by electron beam lithography
A resist pattern with a wide width was formed.

Next, the Cr film, which is the underlying layer of PMMA, was wet-etched with seric ammonium nitride.

Next, using this Cr pattern as a mask, the W underlying the Cr layer was patterned by dry etching. At this time, the dry etching conditions were: power 100W, CF
, gas flow rate of 20 CCM, pressure of 4 x 10-'torr, and S Fa gas flow rate of 50 CCM.
Etching was carried out under two isotropic etching conditions, ie, pressure 2.times.10@-2 Torr, and these conditions were alternately changed at fixed time intervals until the amount of W etched reached 400. The substrate was water-cooled during dry etching to prevent the substrate temperature from rising.

The obtained W Xi! When the cross-sectional shape of the absorber pattern was observed with a scanning electron microscope (SEM), the W absorber pattern had a trapezoidal and pyramidal cross-sectional shape with respect to the substrate as shown in the first figure. Further, the angle of the side wall of the X-ray absorber pattern with respect to the base substrate at this time was 87°.

As shown in FIG. 1, the angle is defined as the angle formed by a straight line connecting the etches at the bottom of the pattern and the etches at the top of the pattern with respect to the base substrate.

Example 2 The same experimental substrate as in Example 1 was used.

Next, a film of Ta, which is an X-ray absorber, was formed on this substrate to a thickness of 0.8 μm by sputtering. Furthermore, on top of this
A Cr film was formed to a thickness of 300 mm by electron beam evaporation as a mask material during etching of a.

After that, as in Example 1, 0.5% of PMMA was added on top of this.
After forming a resist pattern with a width of 0.25 μm by μm μm bispin coating and electron beam writing, the Cr film of the PMMA underlayer was wet-etched with seric ammonium nitride.

Next, using this Cr pattern as a mask, the underlying Ta layer was patterned by dry etching. At this time, the trial etching conditions were as follows: power 100W, CBrF
3 gas (I (contains 2 gases) 0%) flow rate 25 CCM, pressure 4XIO-'torr, anisotropic etching quantity requirements, and C
BrF3 gas flow rate 50CCM, pressure 2X10-2tor
By setting two isotropic etching conditions of r and changing the conditions alternately at fixed time intervals, the amount of Ta etched
We continued etching until we reached 00 people. The substrate was water-cooled during dry etching to prevent the substrate temperature from increasing.

When the cross-sectional shape of the obtained Ta absorber pattern was observed with a scanning electron microscope (SEM), it was found that < Ta
The X-ray absorber pattern had a trapezoidal and pyramidal cross-sectional shape with respect to the substrate. Further, the angle of the sidewall of the Ta pattern with respect to the base substrate at this time was 85°.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing sidewall angles of an X-ray absorber pattern formed by the method of the present invention. 1: Silicon wafer 2: X-ray transmission film 3: X-ray absorption pattern

Claims (1)

[Claims] (1) A method for manufacturing an X-ray mask structure including a step of forming an X-ray absorber in a desired pattern on an X-ray transparent film,
A method for manufacturing a lithography mask structure, characterized in that anisotropic etching and isotropic etching are performed alternately when forming the X-ray absorber pattern by a dry etching method.