JPH02252231A - Fine pattern forming method - Google Patents

Abstract

PURPOSE:To accurately form a fine pattern by projecting low acceleration electron beam on a polymer organic film being a lower layer film of multilayer resist or an inorganic polymer film being an intermediate layer of the multilayer resist or resist. CONSTITUTION:On a semiconductor substrate 1, an polymer organic film as a lower layer film 11 is spread in a specified thickness, and subjected to open baking at a specified temperature for a specified period. Electron beam 12 with dosage of 1000muc/cm<2> projected collectively on the whole surface by an acceleration voltage of 2kV. An intermediate film 13 and an electron beam resist 14 are spin-coated in the respective specified thicknesses, and subjected to electron beam exposure under the acceleration voltage of 20kV and the dosage of 100muc/cm<2>. Successively by using a resist pattern 14P as a mask, the intermediate layer 13 and the lower layer film 11 are etched, thereby forming a very fine pattern of vertical shape whose aspect ratio is high.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fine pattern forming method for forming an arbitrary resist pattern for high precision fine processing on a semiconductor substrate by direct writing with a charged beam.

2. Description of the Related Art Conventionally, in the manufacture of ICs, LSIs, etc., patterns have been formed by photolithography using ultraviolet rays. In recent years, electron beam direct writing technology has come to be used to miniaturize the pattern dimensions of LSI devices and to manufacture ASICs. Electron beam resists used for pattern formation generally have poor dry etch resistance, and pattern resolution deteriorates due to the proximity effect caused by reflection of the electron beam from the substrate. Therefore, multilayer resist methods are used in electron beam lithography. is used. FIG. 5 is a diagram illustrating a multilayer resist process in electron beam lithography. In order to suppress the proximity effect, a polymeric organic film with a thickness of 2 to 3 μm is used as the lower layer film 51.
An inorganic film such as 5i02 or SOG is applied to a thickness of 0.2 μm as an intermediate layer 52, and an electron beam resist 53 is applied to a thickness of 0.5 μm as an upper layer (FIG. 5(a)).

After drawing the pattern, it is developed to form a resist pattern (FIG. 5(b)). Next, using this resist pattern as a mask, dry etching of the intermediate layer 52 is performed (fifth
5(e)), then dry etching of the lower film 51 is performed using the intermediate layer as a mask (FIG. 5(d)). By using the multilayer resist process as described above, fine patterns can be formed with a high aspect ratio. Among the multilayer resist methods, the two-layer resist has a structure in which an inorganic resist or a silicon-containing resist that does not mix with the organic polymer film is coated on top of the organic polymer film, and the three-layer resist has a structure in which the organic resist is coated with an inorganic resist or a silicon-containing resist that does not mix with the organic polymer film. It has a structure in which an inorganic film, mainly 5i02 or organic polysiloxane IIJI (SOG), is formed between the film and the resist, both of which serve to suppress the proximity effect due to reflection of electrons from the substrate. However, since the organic film in these multilayer resists is extremely thick, a new problem has arisen (that is, the charge-up effect of electrons due to the insulating film. As this accumulates, patterns cannot be accurately drawn due to pattern deviations, batting errors, field deviations, etc.

Problems to be Solved by the Invention As mentioned above, in electron beam lithography, there are problems such as low dry etch resistance of electron beam resists and proximity effects due to electrons, and attempts are being made to solve them by using multilayer resists. However, when the multilayer resist method is used, since the insulating film such as the resist is thick, the electron charge-up effect becomes noticeable, making it difficult to accurately draw a pattern. In order to solve this problem with multilayer resists, metals, particularly metal thin films with high conductivity, are used for the intermediate layer. For example, instead of SOG, 5i02, Si,
By using a metal thin film such as W or Ae as an intermediate layer, charge-up can be prevented and accurate pattern drawing can be performed. However, since metal is used in the resist process, there is a problem of contamination. In addition, since the metal must be sputter-deposited, the process becomes complicated and difficult, and there are process problems such as etching the metal after pattern formation and peeling off the metal. Problems such as alignment becoming difficult arise due to a decrease in reflected secondary electrons.

Furthermore, even when electron beam lithography is performed using a single-layer resist with high dry etch resistance, electrons are accumulated in the thick resist or in the insulating film of the substrate, causing charge-up, resulting in pattern shift and connection. Due to misalignment, misalignment, etc., it becomes impossible to accurately draw the pattern. Therefore, a metal thin film such as Ae is formed on the resist film to prevent charge-up. 6th
The figure is a diagram illustrating a single-layer resist process in electron beam lithography. A 1.5 μm thick electron beam resistor 1 with high dry etch resistance is deposited on the semiconductor substrate 1.
After thick coating and heat treatment, a thin aluminum film 62 of 100A is deposited to prevent charge-up (Fig. 6(a)).
. After drawing, the aluminum layer 62 is removed with an alkaline aqueous solution (FIG. 6(b)), and then developed (FIG. 6(C)). By using the process described above, it is possible to form an accurate resist pattern that does not cause pattern displacement due to charge-up. However, since the metal must be sputter-deposited, the process becomes difficult and complicated, and problems such as metal contamination arise, making it impractical.

In order to solve these problems, the present inventors completed a fine pattern forming method in which the entire surface of the film is irradiated with an electron beam without using a metal thin film to prevent charge-up during drawing.

Means for Solving the Problems In other words, the present invention involves applying low-acceleration electron beam irradiation to the underlying polymeric organic film before direct electron beam writing using a multilayer resist method, or by applying low-acceleration electron beam irradiation to the underlying polymeric organic film, or by applying low-acceleration electron beam irradiation to the intermediate layer. This is a method in which an inorganic polymer film is irradiated with a low-acceleration electron beam to increase its conductivity, perform electron beam exposure, and charge up with electrons, thereby forming an accurate fine pattern.

In addition, by irradiating the entire surface of the resist film with a low-acceleration electron beam before performing electron beam writing using a single-layer resist, it is possible to increase the conductivity of the resist surface and prevent charge-up during writing. , accurate fine patterns can be formed.

By irradiating a polymer film with a high-dose electron beam at low acceleration, the conductivity of the surface of the polymer film can be increased. By performing irradiation with an accelerating voltage of 2 KV and 2000 μc/cd, the sheet resistance of the polymer membrane surface was
X It can be made less than 108Ω/mouth. By using this polymer film, incident electrons during electron beam writing travel through the highly conductive film, eliminating charge-up of electrons and making it possible to form accurate fine patterns.

Operation The present invention can increase the conductivity of the film surface and form an accurate fine pattern that does not easily cause charge-up by using the above-described process. In particular, since electron beam irradiation can be performed in the atmosphere, it can be done in-line, and there is no need to evaporate a metal layer, there is no problem of contamination, and the process can be simplified. Charge-up can be prevented and accurate fine patterns can be formed. Therefore, by using the present invention, when performing electron beam direct writing, it is possible to effectively form accurate, high-resolution fine patterns.

Embodiment An embodiment of the present invention is shown in FIG. A polymeric organic film is applied to a thickness of 2 μm as a lower layer film 11 on a semiconductor substrate 1 (often having an insulating film, a conductive film, etc. formed on the surface), and
Bake in the oven at 0°C for 30 minutes. From above, the entire surface was irradiated with an electron beam 12 at an accelerating voltage of 2 KV and a dose of 1000 μc/crd (FIG. 1(a)). Next, SGO is used as the intermediate layer 13, and then electron beam resist 1 is applied.
PMMA (polymethyl methacrylate) as 4,
0.2 μm thick and 0.5 μm thick spin code, respectively.
Accelerating voltage 20 KV, dose 100μc/c-
Electron beam exposure was performed (FIG. 1(b)). The polymeric organic film irradiated with an electron beam is altered by about 0.4 μm from the surface and has high conductivity. Therefore, M I B K
When development was carried out for 2 minutes with a mixture of (methyl isobutyl ketone) and IPA (isopropyl alcohol), an accurate fine pattern was formed (Fig. 1 (C)). Using this resist pattern 14P as a mask, the intermediate layer SOG
By etching the underlying polymeric organic film, we were able to form a vertical, high aspect ratio, 0.25 μm line-and-space ultra-fine pattern (Fig. 1 ω).
). Note that the intermediate layer 13 may be any other insulating film as long as it serves as an etching mask for the lower film 11, but is preferably an organic film containing silicon in order to obtain an etching selectivity.

As described above, according to this example, when electron beam direct writing is performed using a three-layer resist in which the lower layer organic polymer film is irradiated with a low-acceleration electron beam, charge-up can be prevented and accurate fine-grained writing can be achieved. A pattern can be formed.

Next, a second embodiment of the present invention is shown in FIG. A polymeric organic film is coated to a thickness of 2 μm as the lower layer 21 on the semiconductor substrate 1 and heat-treated at 250° C. for 30 minutes, and on top of this, SOG is heat-treated as the intermediate layer 22 at 220° C. with a thickness of 0.2 μm μm. From above, the entire surface is to be irradiated with an electron beam 23 at an acceleration voltage IKV irradiation dose of 1000 .mu.c/c- (FIG. 2(a)). Next, as the upper electron beam resist 24, a PMMA resist was baked with a 0.5 μm μm bispin code at 200° C. for 20 minutes, followed by an acceleration voltage of 20 KV and a dose of 100 ttc/cor.
Electron beam exposure was performed (FIG. 2(b)). The intermediate layer SGO irradiated with the electron beam is altered by about 0.15 μm from the surface, and its conductivity is increased. Therefore, when development was performed for 2 minutes with a mixed solution of MIBK and IPA, an accurate fine pattern was obtained without any pattern shift due to charge-up (FIG. 2(C)). Using this resist pattern 24P as a mask, the intermediate layer SOG and the lower layer organic polymer film are etched to form a vertical, high aspect ratio, 0.25 μm line-and-space ultra-fine pattern. Figure (d)). The intermediate layer 22 may be any other insulating film as long as it serves as an etching mask for the lower film 21, but an organic film containing silicon is preferable in terms of etching selectivity.

As described above, according to this example, when electron beam direct writing is performed using a three-layer resist in which the interlayer film is irradiated with a low-acceleration electron beam, the charge-up that conventionally occurs can be prevented. , an accurate 1a thin pattern can be formed.

Next, a third embodiment of the present invention is shown in FIG. A polymeric organic film is applied to a thickness of 2 μm as a lower layer film 31 on the semiconductor substrate 1, and baked at 250° C. for 30 minutes. From above, the entire surface was irradiated with an electron beam 32 at an acceleration voltage of 3 KV and a dose of 1000 μc/cd (FIG. 3(a)).

Next, a silicon-containing resist was applied to a thickness of 0.3 μm as the upper electron beam resist 33, and after baking on a hot plate at 100° C. for 2 minutes, electron beam exposure was performed at an acceleration voltage of 20 KV and a dose of 10 μc/cor. Figure (b)). The organic polymer film irradiated with the electron beam is altered in quality by about 0.5 μm from the surface, and its conductivity is increased. Therefore, when the film was developed for 60 seconds using a special developer, an accurate fine pattern was formed (Fig. 3 (C)). Using this resist pattern 33P as a mask, the underlying polymeric organic film was etched to form an ultra-fine vertical pattern with a high aspect ratio of 0.25 μm line and space (Fig. 3(d) )).

As described above, according to this example, by irradiating the lower layer of the two-layer resist with an electron beam, charge-up during electron beam direct writing can be prevented and accurate fine patterns can be formed. I can do it.

Next, a fourth embodiment of the present invention is shown in FIG. AZ1400 is applied as an electron beam resist 41 on the semiconductor substrate 1;
It was coated to a thickness of 5 μm and hot plate baked at 100° C. for 2 minutes. Accelerating voltage 2 KV from above
The entire surface was irradiated with an electron beam 42 at a dose of 1000 μc/cI+1 (FIG. 4(a)).

Next, the acceleration voltage was 20 KV and the dose was 20 t.
Electron beam exposure was performed at tc/ca (Fig. 4(b)
), the electron beam irradiated resist is approximately 0.0 mm from the surface.
The quality has changed by about 2 μm, and the conductivity has increased. Next, after removing 0.2 μm of the degraded layer on the surface of the resist by dry etching, development was performed with an organic alkaline aqueous solution, and an accurate fine resist pattern without pattern shift due to charge-up could be formed. (Figure 4 (
C)).

As described above, according to this embodiment, when direct electron beam writing is performed on a single-layer resist, the resist surface is irradiated with a low acceleration electron beam to increase the conductivity of the resist surface and charge up during writing. It is possible to prevent the formation of accurate fine resist patterns.

As described in detail, according to the present invention, a low-acceleration electron beam is applied to an organic polymer film used as a lower layer film of a multilayer resist, an inorganic polymer film used as an intermediate layer of a multilayer resist, or a resist. By irradiating
It can prevent pattern misalignment, splicing misalignment, misalignment, etc. due to charge-up that occurs during direct electron beam writing, and can form accurate fine patterns, greatly contributing to the production of ultra-high-density bonded circuits. I can do Shikoshichi.

[Brief explanation of drawings]

Fig. 1 is a process sectional view of the first embodiment of the present invention, Fig. 2 is a process sectional view of the second embodiment, Fig. 3 is a process sectional view of the third embodiment, and Fig. 4 5 is a cross-sectional view of the process of the fourth embodiment, FIG. 5 is a cross-sectional view of the conventional multilayer resist method, and FIG. 6 is a cross-sectional view of the conventional single-layer resist method. 1... Semiconductor substrate, 11.21... Lower layer film, 13.22... Intermediate layer, 12.23...
...Electron beam, 14.24...Electron beam resist. Name of agent Patent attorney Shigetaka Awano 1 person Figure 1 1--1 γ11: I] To, Koshi; 3; +4P-Rujis Y Ha' Darts 24P--Regis Ha19-S Fig. 1'p34 3f---Lower April 33-'ll) Run over the darts -・tl-,! 33p--Turn at Reliston! 1 Lower layer mode play 53P---Register/Y'terno figure 4flll---1, same line, next turn 63-chamber)
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Claims (4)

[Claims] (1) A process of applying an organic polymer film on a semiconductor substrate and heat-treating it, and then irradiating it with an electron beam all at once; forming an inorganic insulating film on the organic polymer film and heat-treating it; A step of applying a resist film for a charged beam to the surface and heat-treating the resist film, a step of drawing a pattern on the resist film and developing it, a step of etching the inorganic insulating film using the resist pattern as a mask, and a step of etching the inorganic insulating film pattern as a mask. and etching the polymeric organic film. (2) A step of applying an organic polymer film on the semiconductor substrate and heat-treating it; a step of applying an inorganic insulating film on the organic polymer film and heat-treating it; and then irradiating the inorganic insulating film with an electron beam all at once; A step of applying a resist film for a charged beam to the surface and heat-treating the resist film, a step of drawing a pattern on the resist film and developing it, a step of etching the inorganic insulating film using the resist pattern as a mask, and a step of etching the inorganic insulating film pattern as a mask. and etching the polymeric organic film. (3) After applying a polymeric organic film on a semiconductor substrate and heat-treating it, a step of irradiating it with an electron beam all at once; a step of applying an inorganic resist film on the polymeric organic film and heat-treating it; and a step of applying a pattern to the resist film. A method for forming a fine pattern, comprising the steps of drawing and developing the resist pattern, and etching the organic polymer film using the resist pattern as a mask. (4) A step of applying a charged beam resist film on a semiconductor substrate and heat-treating it, a step of irradiating the entire surface of the resist film with a low-acceleration electron beam, and a step of drawing a pattern on the resist film and developing it. A fine pattern forming method characterized by comprising: