JPS6292438A - Forming method for pattern - Google Patents

Abstract

PURPOSE:To form a super-fine pattern by forming a mask of two types of films having equal amplitude of transmitting lights or X-rays and or its odd times of phase difference, thereby obtaining high resolution to the degree of wavelength. CONSTITUTION:When transmitting waves (lights or X-rays) from com4ponent substances 7, 8 adjacent in equal width of a mask 3 made of the substances 7, 8 of mask patterns of difference substances have equal amplitude and phases of pi or its odd times different, transmitting intensity distribution obtained on a resist film 2 becomes as shown. That is, the lights or X-rays which arrive at points X1, X2 on the film 2 corresponding to the boundary of the substances 7, 8 through the portions of the substances 7, 8 cancel each other so that the intensity becomes zero. This is irrespective of a distance (g) between the mask 3 and the film 2 and the size of the pattern. Thus, high resolution to the order of the wavelength can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method for forming a pattern of a semiconductor element, a magnetic bubble element, two concave lattices, etc. using a mask.

[Conventional technology]

Conventional pattern forming methods include photolithography using light (ultraviolet rays, deep ultraviolet rays, etc.) as a light source and xtJiI lithography using soft X-rays.

The principles of these phosphorography techniques are schematically shown in FIG. That is, a film sensitive to light or X-rays formed on a substrate 1 such as a semiconductor wafer, such as a resist film 2 (
The pattern 6 of the mask 3 is transferred to the inside of the cylinder by exposing it to light or X-rays 4 through the mask 3. Here, the conventionally used mask 3 has a thickness that is opaque to light or X-rays, a viscous material (
It has a structure in which the pattern 6 is formed by a material (referred to as an absorber). That is, of the light or X-rays incident on the mask 3, only those incident on the portions where there is no absorber pass through the mask 3 and reach the surface of the resist film 2, and the pattern 6 is transferred thereto.

[Problem that the invention seeks to solve]

In such a pattern transfer method, it is inevitable that the pattern will be affected by the diffraction phenomenon. In other words, the light or X-rays are diffracted even into the portion of the resist film 2 facing the absorber portion, which should not be exposed, causing an exposure effect, and as a result, the resolution is reduced. The influence of diffraction can be reduced by reducing the distance g between the mask 3 and the resist film 2. However, the distance g is at least lopm or more, practically several tens of lobes, in order to prevent mutual movement for alignment and to protect the mask 3 from contamination or damage.
gm is necessary.

For this reason, the minimum dimension of a pattern that can be transferred is around lpm in photolithography, and in X-ray phosphorography, even when using synchrotron radiation light, which is considered to be the most excellent radiation source for lithography. 0
．． The limit is about 27zm.

This invention was made to solve the above problems, and the pattern forming ability of this invention based on a principle different from the conventional technology is that the amplitude of transmitted light or X-rays is equal. , a mask is constructed from two types of films with a phase difference of π or an odd multiple thereof, and light or X-rays are exposed through this mask to form a pattern corresponding to the transmitted intensity distribution caused by the phase difference. It is formed on a film that is sensitive to light or X-rays.

[Effect]

In this invention, since the mask is formed of two types of films in which the amplitudes of the transmitted light or X-rays are equal and the phase difference is π or an odd number multiple thereof, regardless of the distance between the mask and the resist film, Ultra-fine patterns can be formed because high resolution up to the wavelength can be obtained.

〔Example〕

FIGS. 1(a) to 1(d) are sectional views showing the principle of this invention.

First, as shown in FIG. 1(a), constituent substances (hereinafter simply referred to as constituent substances) 7 of a mask pattern made of different substances.
, 8 are adjacent to each other with the same width as shown in the mask diagram (b). That is, each point Xl on the resist film 2 corresponding to the boundary with the constituent substances 7 and 8 passes through each part of the constituent substances 7 and 8.

Since the light or X-rays reaching X2, X3, . . . have a phase difference of π or an odd multiple thereof, they cancel each other out, and as a result, the intensity becomes zero. Such a phenomenon is independent of the distance g between the mask 3 and the resist III 2 and the pattern dimensions (in the case of FIG. 1, the width of the constituent material 7.8).

Therefore, there is no reduction in resolution due to an increase in distance g or limitations on resolution due to diffraction, as in conventional techniques, and according to theoretical analysis, high resolution up to the wavelength level is possible.

The structure of the mask 3 is not limited to the one shown in FIG. 1(a), but may also include an absorber 9 located between the constituent materials 7 and 8 as shown in FIG. 1(C). , even if the mask substrate 10 is provided with a uniform thickness to increase mechanical strength, or even if it does not have a periodic structure as shown in FIG. 1(d), the conditions regarding the amplitude and phase difference described above are satisfied. A similar effect can be obtained if

The material and thickness of the pattern portion of the constituent material 7.8 shown in FIG. 1 can be determined based on the following considerations.

First, the rule 11 for the amplitudes of transmitted waves in two substances a and b to be equal is: 1, IL, 1=ti, μ, ......
・・・・・・・・・(1) Here, tl is the thickness and attenuation coefficient, and the subscripts a and b indicate that they belong to the respective substances (in the following description, the subscripts a and b have the same meaning.
). On the other hand, the condition for the phase difference to be π is 2((n
,, -1) $6-(nL-1) tl, )/in = 1
-(2) Here, n is the refractive index and λ is the wavelength. It is sufficient to select a combination of substances a and b that simultaneously satisfies the following two equations and that J and J have realistic values for mask production.

Next, as an embodiment of the present invention, a combination of silicon nitride and a gold film will be described below. In order to satisfy the above conditions, the film thicknesses of silicon nitride and gold must be 2.37gm and 0.16#Lm, respectively, when the input is lnm.
That's fine. Such a mask 3 can be manufactured by the method shown in FIG. First, a second
Create the structure shown in Figure (a). Here, 11 is a substrate such as a silicon wafer, 10 is a mask substrate made of a film of silicon nitride, poron nitride, polyimide, etc., and 12
13 is a thin metal film such as gold, and 13 is a thickness 2 that forms a pattern.
．． It is a silicon nitride film of 37 gm, and is removed by direct exposure using a focused ion beam, light, electrons, X-rays, etc., or by etching from the back side, as shown in Figure 2(b). A mask 3 having a similar structure can be obtained. Here, the metal film 12 and the mask substrate 1o are not related to the phase difference of transmitted waves between the silicon nitride film 13 and the gold film 14 forming the pattern. Therefore, each thickness can be freely selected within a range that meets the respective objectives of improving the adhesion of the gold film 14 and increasing its mechanical strength.

As a second embodiment of this invention, aluminum (AIL)
) and polymethyl methacrylate (PMMA) will be explained using cross-sectional views shown in FIG. The thickness of each film to satisfy the conditions is 2.16 gm for AI:L film and 2.0 gm for PMMA film.
It is 77zm. Such a mask 3 can be manufactured by the method shown in factor 1.

First, a PMMA film 15 having a thickness of 2.1671 m or more and having an opening is formed by a method similar to that described in connection with FIG. , the structure is as shown in FIG. 3(a). Alternatively, the An film 16 with a thickness of 2.16 pm has an opening.
A PMMA film 15 having a substantially flat surface is formed by spin-coating a PMMA solution thereon to obtain a structure as shown in FIG. 3(b). For the structure shown in FIG. 3(a) or (b), plasma etching using a gas such as oxygen, which hardly etches the An film 16, or reactive ion etching is performed to etch the PMMA. By reducing the film thickness of the film 1°5 to 2.07 pm and further removing the substrate 11 from the back side by etching or the like, a mask having the desired structure as shown in FIG. 3(C) can be obtained. can.

According to the results of theoretical studies regarding the embodiment described in L, even if there is an error of about ±10% in the film thickness of each mask constituent material, it has almost no effect on the pattern transferred to the resist. Furthermore, the film thicknesses, material combinations, and mask manufacturing methods shown in the Examples are some of the possible choices, and the present invention is not limited to these.

〔Effect of the invention〕

As explained above, in the present invention, a mask is constructed of two types of films in which the amplitude of transmitted light or X-rays is equal and the phase difference is π or its raku number times, and the light is transmitted through this mask. Alternatively, the film is exposed to X-rays and formed into a film that is sensitive to light or X-rays with a pattern that corresponds to the transmitted intensity distribution caused by the phase difference, so there is no limitation on resolution due to diffraction phenomena as in conventional technology. In principle, it is possible to form ultra-fine patterns up to the 4° method, which is about the same as the wavelength.

Furthermore, since the distance between the mask and the wafer does not affect the formed pattern, it is possible to close this distance to the limit or precisely control it as in the prior art. 2(a) and 2(b) show a cross-section of an acid material according to an embodiment of the present invention, 9 is an absorber, 10 is a mask substrate, 11 is a substrate, 12 is a metal film, 13 is a silicon nitride film, and 13a is an open film. The holes, 14 are gold 1j1.15 are PMMA membranes, and 16 are A membranes.

Figure 1 21st Figure 3

Claims (1)

[Claims] A mask is constructed of two types of films such that the amplitude of transmitted light or X-rays is equal and the phase difference is π or an odd multiple thereof, and the light or X-rays are exposed through the mask to change the phase difference. 1. A method for forming a pattern, comprising forming a pattern corresponding to the transmitted intensity distribution caused by the transmitted light or X-rays on a film sensitive to the light or X-rays.