JPS6262523A - Pattern forming method - Google Patents

Abstract

PURPOSE:To largely improve the stability and reliability of forming a pattern by sufficiently baking a reflection preventive film at high temperature, then drying the coating resist in vacuum, further exposing, developing and etching to prevent the resist from deforming. CONSTITUTION:In a method of forming a pattern having the step I of forming a reflection preventive film on an article to be etched, the step III of forming a resist layer on the reflection preventive film, the step V of exposing and developing the resist layer to pattern it, and the step VI of selectively etching the article, the step II of baking in advance at high temperature so as not to remove the preventive film by developing the resist layer and the step IV of drying in vacuum the resist layer are provided. In other words, the reflection preventive film is applied on a high reflection metal base layer, sufficiently baked at high temperature, the resist layer is applied, dried in vacuum, exposed and then developed to form a resist pattern, and the preventive film and the base layer are eventually etched by reactive ion etching by allowing the preventive film to remain.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method. The pattern forming method of the present invention can be applied, for example, to manufacturing semiconductor devices (manufacturing very large scale integrated circuits).

[Summary of the invention]

In the pattern forming method of the present invention, the anti-reflection film is sufficiently baked at high temperature, the applied resist is vacuum-dried, and further exposed, developed, and etched to prevent deformation of the resist and form a pattern. This greatly improves the stability and reliability of the system.

[Conventional technology]

Conventionally, when forming a fine pattern on a highly reflective underlayer (object to be etched), an anti-reflection film is applied and painted, a resist is applied and painted in sequence, and then exposure and development are performed. At the same time, each layer including the base layer was removed at the same time.

That is, conventionally, when patterning metal wiring such as Aβ on a semiconductor substrate, it is necessary to pattern the metal wiring on the semiconductor substrate! etc. under metal +I!
After laminating layers, a positive type photoresist is applied directly onto the underlayer, and then exposed using a predetermined mask. However, since the base layer of A1 has high reflectivity, there was a risk that the exposure would be insufficient.

For this reason, an anti-reflective film such as ARC (trade name of Brewer Science, mainly made of polyimide) is applied directly onto the base layer, and then the anti-reflective film is baked at a predetermined temperature (168°C). After that, the resist coated on the anti-reflection film is baked at 90 to 100°C, and then the anti-reflection film and the A1 underlayer are melted when exposed and developed using a reduction projection exposure device. Ta. In this method, the antireflection film is soluble in an alkaline developer that is a resist developer, and as the haking temperature increases, the development speed decreases and hardens; Taking advantage of this property of increasing the amount of water, the dissolution rate of the antireflective film in an alkaline developer is adjusted by controlling the baking temperature of the antireflective film. According to this method, 4.
By uniformly baking the antireflection film at a certain optimum temperature, even the underlying layer can be dissolved during resist development. However, with this method of controlling the baking temperature, it is difficult to achieve uniform baking in large-diameter wafers even if a high-precision baking device is used, so the degree of baking varies depending on the location, and in some areas the reflection The dissolution rate of the anti-reflective film is fast, so the undercut of the anti-reflective film becomes large after development and the upper resist layer peels off, and the dissolution rate becomes slow in other areas, causing the anti-reflective film to remain after development. There were problems with the stability and reliability of the process, such as the formation of scum. FIG. 3 shows a state in which an undercut is formed in the antireflection film, where 2 represents the base layer, 3 represents the antireflection film with the undercut, and 4 represents the resist. Also, areas where the dissolution rate is fast (areas where the developing temperature is low)
Then, due to poor adhesion between the resist and the ARC, the ARC
Even a slight undercut in the pattern often causes the resist to peel off due to a decrease in the contact area with the resist, reducing the stability and reliability of patterning.

In addition, with the conventional method of baking the anti-reflective film at about 168°C, the anti-reflective film is not sufficiently cured, and when the resist is baked, mixing occurs at the interface between the two, resulting in the shape of the resist after development. However, as shown in Figure 3, there was a risk that the area would become stagnant. Such a shape not only poses a problem in terms of patterning accuracy, but also in that it reduces the resolution of the process.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, it was difficult to uniformly control the paking temperature over the entire surface of the anti-reflective film, which caused variations in the adhesion between the resist and the anti-reflective film, resulting in poor patterning stability and reliability. Another problem was that simply painting the anti-reflection film and resist cannot prevent mixing at the interface between the two, resulting in deterioration of the shape of the resist after development, resulting in various inconveniences. .

The purpose of the present invention is to uniformly heat the anti-reflective film to a high temperature and then dry the resist in vacuum, thereby preventing peeling of the resist from the anti-reflective film and deterioration of the shape of the resist, thereby improving the stability and reliability of patterning. The present invention provides a pattern forming method that can be improved.

[Means for solving problems]

The pattern forming method of the present invention includes a step I of forming an antireflection film on an object to be etched, a step II of forming a resist layer on the antireflection film, and exposing the resist layer to light, as illustrated in FIG. , a pattern forming method comprising a step of developing and patterning; and a step of selectively etching the object to be etched; Step 1 of vacuum drying the resist layer
The above object can be achieved by having the following.

[Action of the invention]

That is, in the present invention, a resist pattern is formed by coating an antireflection film on a highly reflective metal base layer, baking it at a sufficiently high temperature, and applying and drying a resist layer in vacuum, followed by exposure and development. Finally, the anti-reflective film and the underlying layer were etched using reactive ion etching (RIE) while leaving the anti-reflective film, resulting in non-uniformity due to the difficulty in controlling the baking temperature of the anti-reflective film. Based on paking, patterning accuracy can be improved by preventing deterioration of the shape of the resist caused by peeling of the resist and anti-reflection film and mixing at the interface between the anti-reflection film and resist.

[Embodiments of the invention]

Hereinafter, the pattern forming method of the present invention will be explained in detail.

Fig. 1 is a flow diagram of the method of the present invention, Fig. 2 (a) to (f)
1 is a process explanatory diagram of an embodiment of the method of the present invention. In this embodiment, as shown in FIG. 2(A), a case will be explained in which a reflective base N (object to be etched) 2 made of Al is laminated on a semiconductor substrate 1 made of Si or the like. (FIG. 2(a) shows the state before step I in FIG. 1.)

Fig. 2 (B) shows the step (2) of spin-coating the anti-reflection film 3 made of ARC on the base N2 (process ILL) and then high-temperature painting.The baking temperature is 180-1
90°C is preferred. Such high-temperature baking enables uniform baking, and by curing the anti-reflection film 3 on the entire surface by high-temperature baking, the solubility of the positive resist to be applied in the next step in an alkaline developer is reduced. can be done.

Figure 2 (c) shows a positive resist (layer) 4 and an anti-reflection film 3.
The process of removing the solvent in the resist by vacuum drying after coating on the resist [[[, shows the state after IV. The vacuum drying temperature is preferably about 25°C. Both high-temperature baking of the antireflection film 3 and vacuum drying of the positive resist 4 are essential, and even if one of them is missing, sufficient effects cannot be obtained. Since the positive resist 4 is used as a mask in the subsequent etching removal, its film thickness is made sufficiently thicker than the antireflection film.

FIG. 2(d) shows a step of exposing the positive resist 4 using the mask 5. As shown in FIG.

Figure 2 (e) shows the PEB used to maintain the shape of the resist.
(Post Exposure Baking) This step can prevent the shoulders of the resist from becoming rounded. The temperature of FEB is preferably about 80°C. Since FEB is performed after exposure, there is almost no possibility that the antireflection film and resist will mix.

FIG. 2(f) shows the structure after the positive resist 4 is developed. In this step (2), a resist pattern is formed on the antireflection film.

Figure 2 (+・) (ch) shows RI E (Reactive
The process (2) is shown in which the antireflection film 3 and the A6 underlayer 2 are sequentially and selectively anisotropically etched by the eI on E Lching method. Since the thickness of the resist 4 is sufficiently thicker than that of the antireflection film, the antireflection film is etched using the resist as a mask. In RIE, for example, ciq-based ions are used.

FIG. 2(S) shows step (2) in which the resist 4 and antireflection film 3 are peeled off and removed using oxygen plasma. This process is the base layer 2
This is done after the etching has been completely removed.

FIG. 2 (N) shows the state in which the A1 wiring batashite is formed.

As described above, in the method of the present invention, the antireflection film 3 is uniformly heated and cured by high-temperature baking, and then the developer of the resist applied thereon is removed by vacuum drying, thereby mixing at the interface between the two layers. At the same time, after developing resist 4, anti-reflection I+733 remains on the entire surface,
Furthermore, since the anti-reflective film 3 and the base layer 2 are sequentially removed by RIE, unnecessary anti-reflective film remains due to variations in hazing, poor adhesion between the anti-reflective film and the resist, and deterioration of the shape of the resist. Deterioration of patterning stability and reliability due to (hemming) can be prevented. Moreover, the antireflection effect of the antireflection film can be fully exhibited, and a highly accurate wiring pattern can be formed without being affected by reflection from the underlying layer.

〔Effect of the invention〕

As described above, according to the pattern forming method of the present invention, patterning is prevented due to unnecessary residual anti-reflective film due to variations in paking temperature, poor adhesion between the anti-reflective film and resist, and deterioration of resist shape. Deterioration in stability and reliability can be prevented, and furthermore, deterioration in resolution as a process can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing the steps of the method of the present invention, and FIGS. B) is an anti-reflection film coating and high temperature baking process, (C) is a resist coating and vacuum drying process, (D) is an exposure process, (E) is an FEB process, (
(f) shows the developing process, (g) and (ch) show the etching process, (su) shows the resist stripping process, and (nu) shows the completed state. FIG. 3 shows a state in which the shapes of the antireflection film and the resist have deteriorated in the conventional pattern forming method. 1...- Semiconductor substrate, 2---- Highly reflective metal underlayer, 3-- Anti-reflection film, 4--
Resist, 5・−・−・−Mask.

Claims (1)

[Claims] 1. A step of forming an anti-reflection film on an object to be etched, a step of forming a resist layer on the anti-reflection film, and a step of patterning the resist layer by exposing and developing it. The pattern forming method includes the step of selectively etching the object to be etched, the step of pre-baking at a high temperature so that the anti-reflection film is not removed by developing the resist layer, and the step of vacuum-drying the resist layer. A pattern forming method characterized by comprising: