JPS6047423A - Method for pattern formation - Google Patents

Abstract

PURPOSE:To obtain the high-accuracy thin film pattern by a method wherein when an organic high molecule layer and a negative resist layer are laminated on the thin film and these layers are etched successively to form openings after which the metallic thin film exposed in the openings are etched. CONSTITUTION:The substrate 1 on which an oxide film is formed is coated with the A thin film 2 to be obtained and further on this substrate, a photoresist film 3 consisting of an organic high molecule layer and an intermediate layer 4 consisting of W and negative photoresist are laminated. Then the substrate is subjected to drawing by an electron beam and development to form openings on the intermediate layer 4 firstly and to form the continuous openings on the film 3 subsequently by reactive ion etching. After that, the thin film 2 is etched by using said openings and the thin film of the desired pattern in which a part of the substrate 1 is exposed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern forming method used in the manufacture of various solid-state devices including integrated circuits, and particularly to a pattern forming method that is effective with multilayer resists.

In recent years, with the increase in the density of LSIs, miniaturization of patterns has been required, and various process technologies for this purpose have been researched and developed. One such example is a so-called multilayer resist consisting of one layer or three layers.

In this multilayer resist, the organic polymer layer formed on the bottom layer effectively flattens the substrate level difference, so the resist layer formed on the top layer is thin and can be applied to a uniform thickness, and furthermore, it can be applied to light exposure. It has the advantage of being able to reduce the standing wave effect due to the influence of reflected light from the substrate in the case of , and the backscattering effect in the case of electron beam exposure. In particular, the three-layer resist has the above-mentioned advantages, and a pattern forming method using this three-layer resist has become indispensable as a technique for high precision and miniaturization of patterns. This three-layer resist is formed as follows. First, as shown in FIG. 1(a), an organic polymer layer 3, an intermediate layer 4, and a resist layer 5 are sequentially laminated on a substrate 1 on which a metal thin film 2 is formed, and then a known exposure and development method is used. Then, as shown in FIG. 7 (bl), a desired pattern is formed on the resist layer 5. Next, as shown in FIG. 1 (C1
As shown in FIG. 3, the intermediate layer 4 is selectively dry etched using the pattern of the resist layer 5 as a mask. This middle layer 4
Generally, Si, 5i02-silicone resin, etc. are used as the etching gas, and a Freon gas such as CF4 is mainly used as the etching gas. Next, as shown in FIG. 1 (dl), the organic polymer layer 3 is dry-etched using the pattern of the intermediate layer 4 as a mask.Oxygen is usually used as the etching gas, and the resist layer 5 is usually made of organic polymer. Layer dry
It is removed during etching. Next, using the formed intermediate layer 4 and organic polymer layer 3 as masks, the metal thin film 2 is selectively dry etched as shown in FIG. When the metal thin film 2 is made of aluminum, CCl4 or the like is used as the etching gas. Further, the opening layer 4 is removed by any wet or dry method before or after etching the metal thin film. And finally, Figure 1
As shown in f), the organic polymer layer 3 is peeled off and removed by, for example, oxygen gas plasma treatment.

By the way, in the conventional pattern forming method as described above,
When etching thin metal films 2t, problems often arise during the etching process. In other words, if the metal thin film 2 is made of aluminum, the time required to start etching, the so-called dead time, becomes longer, and in reality, as shown in Figure 1 (fe), the etching process is longer than the etching process. Kimono 6 is produced. This has a thickness of about θ/μm.

Furthermore, even after the organic polymer layer 3 is peeled off by, for example, oxygen gas plasma treatment, it remains unremovable as shown in FIG. (Surface stabilization) This was a cause of deterioration of device characteristics such as interference with film formation.

Therefore, the two inventors conducted various studies on methods to overcome these drawbacks, and as a result, they came to the following findings.

3J@ In the etching of the organic polymer layer 3 (FIG. 1(d)), which is the final step of resist pattern formation, if an undercut occurs in the organic polymer layer 3, the dimensional accuracy of the pattern formed on the metal thin film 2 will be affected. Since the etching rate is significantly reduced, superior anisotropic etching is required. This etching method is a reactive ion etching method using oxygen gas (
02RIE) is most suitable. Then, in order to completely remove the organic polymer layer 3 to be etched by O2RIE, so-called over-etching is performed. Therefore, in reality, at this stage of over-etching, as shown in FIG. 9, the metal thin film 2 is also exposed to 02RIE, so that oxide 7 is formed on the surface of the metal thin film 2. This oxide 7 is difficult to be etched and is eventually removed by sputtering during dry etching, which takes time. When the metal thin film 2 is made of aluminum, the generated oxide 7 is released into the gas phase by sputtering accompanying dry etching, and this becomes a nucleus to form CH
A polymerization reaction using XCIY as a monomer occurs.

This polymer with the oxide 7 as a core adheres to the steep side surface of the pattern of the organic polymer layer 3. the result.

As mentioned above, it was thought that deposits 6 as shown in FIG. 1 were generated. Therefore, it has been found that this deposit 6 is a mixture of aluminum and organic matter, which makes it extremely difficult to selectively remove only this deposit 6. Therefore, in order to prevent the occurrence of the deposits 6, before etching the metal thin film 2 for pattern formation (thin film etching), remove the oxide 7 that causes the deposits 6.
From the viewpoint that it is preferable to remove the oxide 7 in advance, the oxide 7 is removed along with the surface layer of the metal thin film 2 by wet etching using an alkaline solution or dry etching using hydrogen gas plasma, and then - the metal thin film 2 is removed together with the surface layer. When thin film etching was performed to form the pattern No. 2, it was found that no deposits were observed on the side surfaces of the pattern of the organic polymer layer 3.

The present invention has been made based on the above findings. That is, in the present invention, after patterning an organic polymer layer,
A pretreatment etching step is performed to remove the oxide on the metal thin film along with the thin film surface layer by immersing this sample in an alkaline solution or by dry etching using hydrogen gas plasma.After this pretreatment etching step, the metal thin film is etched. (thin film etching). To explain this using a drawing, after forming a three-layer resist pattern as shown in FIG. 7 (pretreatment etching), the remaining metal thin film 2 is etched as shown in FIG. 6, and the underlying organic thin film is subsequently removed as shown in FIG. The purpose is to obtain a metal thin film pattern free of such deposits.

When removing thin film surface layers by wet etching, the immersion time in an alkaline solution to remove oxides may be less than 7 minutes, thus requiring expensive equipment or long periods of time to remove deposits or oxides. No time process required. As an example of the alkaline solution used, any photoresist developer containing trimethylamine as a main component, which is widely used in the manufacture of semiconductor devices, is suitable.Next, the present invention will be explained in more detail with reference to Examples.

〔Example/〕

First, on a silicon substrate having an oxide film, an aluminum film containing 296 silicon was formed to a thickness of t''ρ6 μm by the Sno(Tsuttaring method).After this, a photoresist AZ-/ manufactured by Shipley Co., Ltd. as an organic polymer layer was formed. 37θ/
Spin coated to a film thickness of jμ2n and heated at −〇θ℃ under nitrogen atmosphere.
At 17:00, I'lJI heat treatment was applied. Next, t! as a middle class! 3μt film thickness tungsten, resist) 7
+7 as 1! , 5μ1121 film thickness) were sequentially formed using an electron beam negative type CMS, and a desired OMS pattern was formed by electron beam lithography and development processing. Next, using a reactive ion etching method using hexagonal sulfur as an etching gas, tonka/θ hidden gas flow rate jθBQQm, pressure αθ,
Using the CMS pattern as a mask at 5 Torr, etching the Gesten, and using a reactive ion etching method using oxygen as the etching gas, the tortoise θ
θW, gas t&R, 50BcQm-pressure θθ/Torr
Mask the tungsten pattern in the dispute! /c and A
Z-737θ was etched. In the etching of AZ-/j7θ, over-etching was performed by 50% of the visually confirmed etching end point time.

Thereafter, the substrate was immersed in an aqueous solution of AZ developer having a volume ratio of /:/ for 7 minutes, washed with water for 7 minutes, and then dried (pretreatment etching step). Subsequently, the aluminum film was dry etched (thin film etching process) using gas plasma consisting of carbon tetrachloride under the following conditions: current JA - gas R, amount 2jθ8 em, pressure θ-2 Torr.

A high 4n degree aluminum pattern with no deposits was obtained.

Although the case where the metal thin film is an aluminum film has been described in this embodiment, the present invention is not limited to an aluminum film. is formed, which significantly impedes the etching of the tungsten film; however, by performing alkaline solution treatment (pretreatment etching), the thin film surface layer containing oxides is removed, allowing smooth thin film etching. In this example, AZ-/
A three-layer resist consisting of 37θ/tungsten/CMS was used, but this method is generally applicable to the multilayer resist method in which Aritoshi's Aritoshi molecule is the bottom layer. If it involves a step of etching the layer to form an oxide on the front side of the thin film.

Therefore, the present invention is applicable to all cases where the gas used for etching the organic polymer layer contains oxygen, which is a factor in the formation of oxides. For example, this is the case when a gas containing oxygen mixed with CCl4, CF4, etc. is used. Further, in this example, an AZgL image solution was used as the alkaline solution, but the same effect can be achieved as long as it is an alkaline solution that can bath-dissolve oxides. For example, solutions or aqueous solutions of potassium hydroxide, calcium hydroxide, calcium carbonate, ammonia, pyridine, etc. can all be applied. Formed aluminum. Example/Similar to ICAZ-/
37θ, tungsten, CMSf:l
Tungsten and AZ-/37θ were each dry etched. After this, Denkoryu 3 A, I (2fiu
it /θθSeem, pressure θ-204tTorr (1
) for 70 minutes (pretreatment etching step). Next, the current JA and CCl4 flow rate 7.58 (40 m
, the aluminum film was dry etched under the conditions of pressure θ22JTorr (thin film etching process), and deposits were generated in the sample without hydrogen gas plasma treatment (pretreatment etching process), but with hydrogen gas plasma treatment No deposits were observed in the strained sample.

As explained above, the present invention relates to a notch formation method for etching a thin metal film using a multilayer resist method, and the present invention solves the problem of inhibiting etching of a thin metal film and furthermore causing deposits. This problem can be solved by removing the surface layer of the metal thin film on the substrate before thin film etching.

Therefore, the present invention makes it possible to form highly accurate thin film patterns that take advantage of the advantages of multilayer resists, and makes it possible to easily form multilayer interconnections on the order of submicrons.

[Brief explanation of the drawing]

Figure 1 ta) to tf) are process cross-sectional views to explain the conventional pattern forming method, Figure 1 is a cross-sectional configuration diagram of the laminate when a thin film pattern is formed using the conventional pattern forming method, @3 Figure 9 is a cross-sectional diagram of the laminated plate after the organic polymer layer has been removed after forming the same thin film pattern, FIG. 9 is a cross-sectional diagram of the S-layer plate when a three-layer resist pattern is formed using the same conventional method, and FIG. 7 to 7 are process cross-sectional views for explaining the present invention, and FIG.
A cross section of a T-layer plate (this is a configuration diagram. 1...Substrate, 2...Total bending thin film, 3...
...Organic polymer layer, 4...Intermediate layer, 5...
...Resist layer, 6... Deposit, 7...
...Oxide. Applicant Nippon Telegraph and Telephone Public Corporation Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (4)

[Claims] (1) etching the organic polymer layer laminated on the metal thin film on the substrate using oxygen-containing gas plasma to form a desired resist pattern on the organic polymer layer;
3. In a pattern forming method comprising a thin film etching step of etching the metal thin film using the fabric polymer layer as an etching mask, before the thin film etching step, a method is applied to the metal thin film along with the formation of the resist pattern. A pattern forming method comprising a pre-etching step for removing the surface layer of the thin metal film containing the generated oxide. (2) The pattern forming method according to claim 1, wherein the pretreatment etching step is a wet etching step performed by immersion in an alkaline solution. (3) The pattern forming method according to claim 2, wherein the alkaline solution is a solution containing trimethylamine as a main component. (4) The pattern forming method according to claim 1, wherein the pre-etching step is a dry etching step using hydrogen gas plasma.