JPS63170917A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To form a form pattern which has improved resolution limit by dividing a photoetching process into two sections and exposing the pattern in every other one. CONSTITUTION:With a first mask having a pattern with period 2L which doubles the period L of a desired pattern, a pattern is formed on the upper layer resist and then it is transferred to an intermediate layer 12 with the reactive ion etching (RIE) method. Thereafter, the intermediate layer 18 and upper resist 17 are coated. Next, with a second mask having the pattern of period 2L, exposure and development are carried out to pattern the upper layer resist 17. Thereafter, it is then transferred to the intermediate layer 18 with the RIE method. Next, with the intermediate layers 12 and 18 used as the mask, the lower layer resist 13 is etched by the RIE method and thereby the pattern of period L can be obtained on the lower layer resist 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a light path method in a photolithography process.

[Conventional technology]

Conventional exposure methods in photolithographic processes are described, for example, in the publication Journal of Vacuum Science and Technology (J, Vac.

When a single pattern is transferred to a photosensitive resin using the reduction projection exposure method shown in Sci. Technol, Vol. 17, No. 5, p.
The light emitted from the light source is focused by a lens and irradiated onto a single mask, and the light that selectively passes through this mask is focused by the lens and imaged onto the wafer. At this time, a photosensitive resin that has been applied on the wafer in advance is exposed to light, and a pattern is transferred to this photosensitive resin through a subsequent development process.

[Problem that the invention seeks to solve]

The exposure method in the conventional photolithography process described above has various problems when transferring fine patterns. One of them is the resolution limit of the exposure optical system. In general, the resolution limit of a reduction projection exposure system is expressed as approximately = 1 ((λ/NA). Here, λ is the exposure wavelength, NA is the numerical aperture of the lens, and k is a proportionality constant determined by the process and is 0.
The limit is said to be around 6.

For example, using a lens with NA=α35, λ=0.435
If m light is emitted from a source of 8 μm, the resolution limit is approximately 0.8 μm.
The value is m. This resolution limit R has gradually improved year by year due to higher numerical apertures of lenses and shorter exposure wavelengths, but rapid improvement is difficult due to lens manufacturing technology, so it is 0.8 μm. There was a drawback that it was extremely difficult to obtain the following pattern.

[Means for solving problems]

The fine pattern forming method of the present invention is a fine pattern forming method in which a mask pattern is transferred to a photosensitive resin layer coated on an object to be etched by exposure and development processing, and the fine pattern forming method is a method of forming a fine pattern with a period twice the period of a predetermined pattern. A step of forming a first pattern having twice the period on the photosensitive resin layer using a first mask having a pattern, and a step of forming a photosensitive resin layer using a second mask having twice the period. The first pattern includes a step of forming a second pattern having twice the period in a state parallel to the first pattern by a predetermined period.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 3 illustrates the principle of the invention. Figure 3 (aJ
Periodic line and space pattern 2 shown in
1, first, as shown in FIG. 3(b), exposure and development are performed using a mask having a pattern 22 with a period of 2L to form a pattern 22. Here, thin line patterns are easily formed. This is because, in general, when forming a pattern using a positive photoresist, the resolution limit is determined by the space dimension, and it is easy to form the space width to be large and the line width to be small.

Next, as shown in FIG. 3(C), exposure and development are performed using a mask having patterns 23 to form patterns 23 between patterns 22, thereby forming patterns 12 at regular intervals. It becomes possible.

FIG. 1 is a sectional view showing the main steps of the first embodiment of the present invention. As shown in FIG. 1(a), a semiconductor substrate 15
A three-layer resist 16 is applied to the upper object 14 to be etched. The three-layer resist 16 is the lower resist 13. Middle layer 12.
It consists of an upper layer resist 11. This intermediate layer 12 is made of spin-
Formed by On-Glass Gin. Next, as shown in Figure 1 (bl), the period 2L is twice the period of the desired pattern.
A pattern is formed on the upper layer resist using a first mask having a pattern, and then transferred to the intermediate layer 12 using a reactive ion etching method (hereinafter referred to as R and IE). After this, as shown in FIG. 1(C), the intermediate layer 18 and the upper resist layer 17 are applied again, and then, as shown in FIG. 1(d), a second mask having a pattern with a period of 2L is used. After performing exposure and development processing to pattern the upper resist layer 17, it is transferred to the intermediate layer 18 using HIE.

After this, as shown in FIG. 1, the intermediate layer 12. Using the intermediate layer 18 as a mask, the lower resist layer 3 is etched by IE to obtain a periodic pattern on the lower resist layer 13. In this way, it is possible to obtain a periodic fine pattern on the object to be etched 14 on the semiconductor substrate 15.

FIG. 2 is a sectional view showing the main steps of a second embodiment of the present invention. The steps up to coating the intermediate layer 18 and the upper resist layer 17 are similar to the steps shown in FIG. 1(C) of the first embodiment. Next, as shown in FIG. 2 (al), the entire surface of the semiconductor substrate is irradiated with deep ultraviolet light, etc., and as shown in FIG. A pattern can be formed in the underlying resist 13.

Above, the embodiments of the present invention have been explained with respect to the simplest line and space pattern, but of course, in addition to the line and space pattern, almost any pattern shape such as an L-shape or a U-shape pattern can be used. The present invention is applicable to Further, although the explanation has been made regarding optical exposure, it is clear that the present invention is also effective for electron beam exposure and X-ray exposure.

〔Effect of the invention〕

As explained above, the present invention divides the photoetching process into two steps and exposes every other pattern separately, thereby forming a fine pattern that is 1/2 times the resolution limit of the conventional exposure method. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main steps of the first embodiment of the invention, FIG. 2 is a sectional view showing the main steps of the second embodiment of the invention, and FIG. 3 is a detailed explanation of the invention. FIG. 11...Upper layer resist, 12...River/middle layer,
13... Lower layer resist, 14... Group/object to be etched, 15... Semiconductor substrate, 16...
・Three layer resist, 17... Upper layer resist, 18
・・・・・・Middle layer, 19・old・・far ultraviolet light, 21・・
. . . desired pattern, 22 . . . pattern formed by first exposure, 23 . . . pattern formed by surface second exposure.・・・－＼ Agent Patent Attorney Susumu Uchihara'..., 1 person, ＼
1〒 Article 3 Figure

Claims (2)

[Claims] (1) In a method for forming a fine pattern in which a mask pattern is transferred to a photosensitive resin layer coated on an object to be etched by exposure and development, a first pattern having a periodicity twice the period of a predetermined pattern is used. forming a first pattern having twice the period on the photosensitive resin layer using a mask; forming a first pattern on the photosensitive resin layer using a second mask having twice the period; A method for forming a fine pattern, comprising the step of forming a second pattern having a period twice as large as the period in which the first pattern is translated in parallel by the period. (2) The photosensitive resin layer includes an upper layer photosensitive resin, an intermediate layer,
It is a three-layer resist consisting of a lower layer photosensitive resin, and the first
2. The method for forming a fine pattern according to claim 1, wherein the second pattern is a pattern formed on the intermediate layer.