JPH0518457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming various opening patterns such as through holes in a groove pattern in the production of semiconductor devices, and in particular, relates to a method for forming various opening patterns such as a groove pattern through holes in the production of semiconductor devices, and in particular, a method for forming various opening patterns such as a groove-like pattern through holes in the production of semiconductor devices. The present invention relates to a method of forming an opening pattern.

[Conventional technology]

The conventional pattern forming method of this type is shown in FIG.
This will be explained using d. First, as shown in FIG. 4a, a film 2 in which openings are to be formed is deposited on a substrate 1,
After forming a predetermined mask pattern 3 made of a resist material or the like on this as shown in FIG. 4b,
The exposed portion of the membrane 2 through the opening 4 of the mask is removed by etching as shown in FIG. 4c. Thereafter, by removing the mask pattern 3, a desired opening pattern 5 as shown in FIG. 4d is obtained.

However, a drawback of this method is that it is not easy to obtain fine openings in the etching of the membrane 2. In other words, reactive ion etching (hereinafter referred to as
A processing method with strong etching directionality, such as RIE (referred to as RIE), is required, but in this type of processing method, the difference in etching rate between different materials, that is, the etching selectivity, is generally small. Therefore, in order to process the film 2 of the required thickness, the thickness of the mask pattern layer 3 must be made as thick as possible. However, in lithography using ultraviolet light or electron beams, which are commonly used to form mask patterns, it is necessary to make the resist mask film as thin as possible in order to resolve fine patterns, and this is a necessary condition for use as an etching mask. It is contradictory. Furthermore, if you try to increase the selectivity as much as possible by adjusting processing conditions such as RIE, the directionality of etching tends to weaken, resulting in undercuts, making it extremely difficult to perform processing that is faithful to the mask dimensions. become.

Furthermore, another problem when using a dry etching method such as RIE is that fine openings tend to be left unetched. This is mainly due to the fact that the etch rate decreases as the aperture size decreases. This decrease in etching rate is particularly noticeable in submicron-width grooves and through-holes. Therefore, when processing a pattern that includes submicron-width openings and openings with dimensions of around 1 μm at the same time, the end of etching is the opening point. It will be different for each. Therefore, it becomes difficult to set the etching time and conditions, and there is a problem in that even slight fluctuations in the conditions tend to cause residual etching.

Further, as another conventional method for avoiding the problems caused by the above-mentioned processing method, there is a technique called lift-off. This lift-off method will be explained with reference to FIGS. 5a to 5c. First, as shown in FIG. 5a, a predetermined pattern 3 made of a resist material or the like is formed on a substrate 1, and a desired material film 2 is formed by vacuum evaporation or the like to a thickness not exceeding the thickness of this pattern 3. It is attached to the entire surface of the substrate from a direction perpendicular to it.
At this time, the film 2 does not adhere to the side surface 6 of the pattern 3 as shown in FIG. It is separated from the attached portion 2-2. Furthermore, by dissolving and removing the pattern 3 through the separation gap between the pattern 3 and the portion 2-2, the portion of the film portion 2-1 on the pattern 3 is removed, and a desired opening pattern is formed as shown in FIG. 5c. 5.

However, this method also applies to the attached film portions 2-1, 2-
In order to reliably separate both parts of 2, use pattern 3.
The thickness of the pattern 3 must be made sufficiently thicker than that of the film 2 to be deposited, and the side surfaces of the pattern 3 must be controlled vertically or with an overhanging slope, so there is a limit to the dimensions of the fine pattern that can actually be formed. Therefore, it is difficult to obtain an opening pattern 5 of any size in the film 2 of a required thickness.

[Problem that the invention seeks to solve]

The present invention solves the conventional problem in which it is difficult to form fine openings in films of arbitrary thickness, as described above, and enables the formation of fine openings in films of various materials for semiconductor devices, regardless of their film thickness. , any opening pattern including extremely fine dimensions can be easily formed. This provides a new lift-off method that utilizes the characteristics of directional film deposition.

[Means for solving problems]

That is, to summarize the present invention, the pattern forming method of the present invention includes forming one micropattern having a substantially bell-shaped pattern cross section on a substrate, or a plurality of adjacent micropatterns having their bottoms substantially in contact with each other and their tops substantially touching each other. At least one of the aggregate patterns arranged with gaps is formed, or at least a pattern having unevenness is formed on the top thereof, and a film thicker than the pattern is applied to at least the area by a directional film deposition method. Based on the characteristic that the deposited film that is attached to the pattern and the substrate and that is in contact with the pattern that has a steep slope (including vertical, overhang, or undercut shape; the same applies hereinafter) is easily etched, first, we It is characterized by selectively removing only the portions to form a predetermined opening pattern in the deposited film. Note that the above-mentioned steep slope also includes the concept of unevenness formed at least on the top of the pattern, which will be described in detail later.

The basic steps of the present invention will be explained using FIGS. 1a to 1d. First, as shown in FIG. 1a, a pattern 3 consisting of minute bell-shaped protrusions or aggregates thereof is formed on a substrate 1 using a material such as a resist. At this time, it is desirable to make the entire pattern as small as possible so that the top of the pattern does not have a flat surface as much as possible, and to form the top to be sharp. Next, as shown in FIG.
is formed to a desired thickness from a direction perpendicular to the substrate 1 by a directional film deposition method such as an ECR plasma deposition method. At this time, due to the dependence of the film quality on the steep angle (including vertical) of the underlying surface, which is a phenomenon peculiar to such directional film deposition methods, the deposited film on a surface tilted or perpendicular to the substrate surface may not be horizontal. The film quality is much more easily etched compared to the film deposited on the surface. Therefore, the film portion 2' grown in contact with the side surface of the pattern 3 shown in FIG. 1b (indicated by a satin finish in FIG. 1b) can be directly etched onto the substrate surface by a slight etching process. The film grown on the pattern 3 or the film grown on the top of the pattern 3 can be easily removed without scraping. Utilizing this property, as shown in Figure 1c, dry or wet etching is performed using an appropriate reactive gas or chemical depending on the type of material film 2 to selectively remove the fragile film portion 2'. Then, the film portion 2-1 on the pattern 3 and the film portion 2-2 on the substrate 1 are separated. Furthermore, as shown in FIG. 1d, the film part is etched by continuing the above etching process until the area of contact between the film part 2-1 and the top of the pattern 3 disappears, or by adding an etching process under separate conditions. 2-
1 from above the pattern 3, or by dissolving and removing the pattern 3 from its exposed side surface by etching or other appropriate processing method, the film portion 2-1 is simultaneously removed, and the remaining film portion 2- 2
A desired aperture pattern 5 is formed using the chisel. In the former case, the pattern 3 remaining inside the opening pattern 5 is removed by appropriate processing as necessary.

Next, other basic steps of the present invention will be explained using FIGS. 2a to 2e. First, as shown in Figure 2a,
A desired pattern 3 made of a material such as resist is formed on a substrate 1. As with the conventional method, this pattern 3 can be simply formed as a figure with the required dimensions, and there is no need to convert it into a set of fine patterns. Subsequently, as shown in FIG. 2b, as fine an unevenness as possible is formed on at least the top surface of the pattern 3 by appropriate processing. In addition, Figure 2a
The steps shown in FIG. 2 and the steps shown in FIG. 2b may be reversed in order. That is, a film having an uneven surface may be formed and then patterned. Furthermore, as shown in FIG. 2c, a desired material film 2 is formed on the surface of the substrate 1 to a desired thickness from a direction perpendicular to the substrate 1 by a directional film deposition method such as an ECR plasma deposition method. do. At this time, a film portion 2″ formed in contact with the side surface and top uneven surface of the pattern 3
(shown as a satin finish in Fig. 2c) is extremely fragile compared to the film formed on the horizontal surface of the substrate 1, and should be subjected to appropriate dry or wet etching treatment as shown in Fig. 2d. can be easily selected and removed. After this, similar to the basic steps of the present invention,
If necessary, the remaining pattern 3 is removed to form a desired opening pattern 5, as shown in FIG. 2e.

According to the basic process of the present invention described above, there is no need for a highly directional etching process such as RIE with low etching selectivity when forming the opening. Therefore,
The thickness of the resist film forming the pattern 3 can be arbitrarily thinned, and the optimal resist film thickness for forming the pattern 3 according to the required minimum opening size can be selected. A fine opening pattern can be formed in the film. Furthermore, the various problems of the prior art described above, such as the absence of any residual material that is likely to occur with RIE, are eliminated, making it extremely easy to realize fine patterns.

[Effect]

As mentioned earlier, the pattern forming method of the present invention takes advantage of the fact that the deposited film on the part of the formed pattern that is in contact with the steep slope is easily etched. In this method, only the weak parts of the film are selectively removed to form an opening pattern in the attached film. Note that the present invention also utilizes the characteristic that the deposited film in the portion that is in contact with the unevenness of the pattern is also easily etched. That is, the concept of the steep slope in the pattern also includes unevenness provided at least at the top of the pattern.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 First, as shown in FIG. 1a, a negative electron beam resist CMS was applied to a thickness of 0.2 μm on the substrate 1.
A predetermined pattern was drawn and developed by an electron beam direct writing method to form a rectangular and linear resist pattern 3 having a minimum dimension of 0.1 μm. At this time, the height of the pattern 3, that is, the remaining film thickness of the resist after development, was about 0.15 μm, and the pattern 3 consisted of one pattern or a set of patterns, each of which had a narrow bell-shaped cross section. Note that the drawing pattern data for the aggregate patterns (the three aggregate patterns on the right side of FIG. 1a) for forming a wide opening were prepared as a set of fine patterns in which the desired figures were densely packed.

As shown in FIG. 1b, a SiO ₂ film 2 of about 0.8 μm in thickness was formed thereon using the ECR plasma deposition method. Next, add buffered hydrofluoric acid solution (1 volume of 50% hydrofluoric acid +
Etching was performed for about 45 seconds in a saturated aqueous solution of ammonium fluoride (9 volumes) to completely remove the portion 2' of the SiO ₂ film 2 that had adhered to the resist pattern and the adhered film on the pattern 3, as shown in Figure 1d. did.
As a result, the deposited SiO ₂ film 2 on the substrate 1 was formed with an opening pattern 5 having side surfaces inclined at approximately 70 degrees with respect to the surface of the substrate 1. The dimension of the opening 5 at the interface of the substrate 1 was almost the same as the bottom dimension of the resist pattern 3 originally drawn, and it was possible to obtain an extremely fine opening of about 0.1 μm. Further, the resist pattern 3 in the opening could be easily removed by ashing by oxygen plasma treatment.

According to the above-described embodiments of the present invention, advantages other than those described above can also be obtained. In other words, the side surface of the opening 5 is not perpendicular to the substrate 1, but has an inclination of about 70 degrees in the case of the above example, so this opening pattern 5 is
If the through hole is used for LSI circuit wiring and the deposited SiO ₂ film 2 is used as an interlayer insulating film, it becomes easy to uniformly adhere the metal film into the through hole when forming the metal wiring.

Further, as another use of the above embodiment, it is possible to apply it to a mask for processing the substrate 1. That is,
The SiO ₂ film 2 formed by the above procedure is used as a mask material,
The exposed substrate 1 is inserted through the opening 5.
By processing with an appropriate method such as RIE, the substrate material can be effectively processed even when resist cannot be used as a mask material due to etching resistance or the like.

Although the above example shows the case where a negative type resist material is used, it is clear that the effect of the present invention is basically the same even if this resist material is used as a positive type material. Whether to use a negative type or a negative type may be selected to satisfy various process requirements such as ease of forming a pattern and ease of creating drawing data or a photomask corresponding to the intended opening pattern.

Next, as another embodiment of the present invention, a method of forming a pattern into a laminated structure of two types of materials is shown in FIGS. 3a to 3e.
This will be shown in the second example below.

Example 2 First, as shown in FIG.
A thin film 6 is formed to a thickness of approximately 0.1 μm, and a minimum dimension of 0.1 μm is formed thereon by the same process as in the first embodiment.
A first mask pattern 3 was formed of a rectangular and linear resist composed of a single bell-shaped pattern or a set of bell-shaped patterns having a film thickness of 0.2 μm and including m.

Subsequently, using this resist pattern 3 as a mask, the poly-Si film 6 was etched away by CF ₄ plasma, producing a slight undercut as shown in FIG. 3b.

Thereafter, as shown in FIG. 3c, a SiO ₂ film 2 was formed to a thickness of about 0.8 μm using the ECR plasma deposition method. At this time, the portion of the SiO ₂ film 2 on the substrate and the portion 2' in contact with the pattern 3 were effectively separated by the undercut gap between the resist 3 and the poly-Si film 6.

As a result, by etching using a buffered hydrofluoric acid solution for a very short time, the portion 2' attached to the resist pattern 3 and the attached film on the pattern 3 are completely removed as shown in FIG. 3d. I was able to do that.

Finally, the resist pattern 3 in the opening 5 was removed by ashing by oxygen plasma treatment to obtain a rectangular and linear opening 5 as shown in FIG. 3e.

According to the second embodiment, by forming an extremely thin and easily processable material film on the substrate, the process of separating the deposited SiO ₂ film can be made easier, more stable and more reliable. There are advantages.
In this example, poly-Si was used as the material film for lamination, but the same effect can be obtained with other materials as long as they can be easily processed using the first mask pattern material as a mask. It is clear that it can be done. Also, any remaining poly in the opening
Since the Si film 6' can be removed extremely easily by CF ₄ plasma treatment, etc., it does not pose any hindrance to subsequent processes, and can also be left in the opening and used as a contact layer between the substrate and the wiring metal. can.

According to the spirit of the method of the present invention, when the material deposited on the pattern is formed by a directional film deposition method, there is a noticeable difference in film quality due to the steep angle of the underlying surface, that is, the pattern, that is, the material is easily etched. Any material that changes can be used, so materials other than SiO ₂ shown in the first and second embodiments, such as silicon nitride, can also be used. It goes without saying that similar effects can be obtained by using an ion beam, X-rays, or ultraviolet rays other than the electron beam shown in the embodiments as the exposure means.

Now, in the basic process of the present invention described above, when it is desired to form a mixture of fine-width patterns and wide-width patterns on the same substrate, as described above, the wide patterns are formed as shown in FIGS. As shown in Figure 3, it is necessary to prepare a densely packed pattern of fine width patterns. In this case, the original photomask pattern or drawing pattern data is
It is necessary to convert and create the required figure as a collection of densely packed fine patterns, and the exposure and development conditions for the densely packed fine patterns must be adjusted so that the entire deposited film deposited on the densely patterned areas can be effectively removed. Must be optimized. An embodiment based on another basic process of the present invention devised to easily realize these various requirements with a large degree of margin will be described with reference to FIGS. 2a to 2e.

First, as shown in FIG. 2a, a desired pattern 3 having a steep slope (vertical in the figure, but may be in an overhang or undercut shape) made of a material such as resist is formed on the substrate 1. This pattern 3 may be formed as a figure with the required dimensions as in the case of the conventional method.

Subsequently, as shown in FIG. 2b, as fine as possible unevenness is formed on the top surface of the pattern 3 by the following appropriate treatment.

Furthermore, as shown in FIG. 2c, a desired material film 2 is deposited on the entire surface of the substrate 1 to a desired thickness from a direction perpendicular to the substrate 1 by a directional film deposition method such as an ECR plasma deposition method. Form.

At this time, the film portion 2'' formed in contact with the side surface and top uneven surface of the pattern 3 is extremely fragile compared to a film formed on a horizontal substrate surface, so as shown in FIG. 2d, It can be easily selectively removed by appropriate dry or wet etching treatment.

After this, if necessary, as shown in Figure 2e,
The remaining pattern 3 was removed to form a desired opening pattern 5.

Note that various methods can be applied as a method for processing the surface of the pattern 3 shown in FIG. 2b to make the surface uneven. For example, by superimposing exposure of a predetermined pattern image on a resist film on which pattern 3 is to be formed and exposure through a fine mesh mask at an appropriate exposure amount ratio, and developing, a fine pattern corresponding to the mesh is formed on the top of the resist film. There is a method of obtaining a predetermined pattern having irregularities. In this method, the order of exposure of the predetermined pattern image and mesh exposure can be arbitrarily selected. Furthermore, after performing the first exposure, development may be performed, and then the second exposure and development may be performed. Furthermore, the same effect can be obtained by forming interference fringes with fine pitches using an interference optical system instead of the mesh exposure. Alternatively, a method other than exposure may be used, such as surface roughening treatment by surface alteration when the resist is irradiated with gas plasma. As is well known, plasma containing inert gas such as Ar gas, halogen-containing gas such as CF ₄ , CCl ₄ , Cl ₂ , or hydrocarbon gas such as CH ₄ , C ₂ H ₆ When organic polymers such as resists are processed, structural and compositional changes occur in the surface molecular layer, resulting in minute irregularities on the surface. Therefore, by subjecting a resist having a predetermined pattern to such a plasma treatment, the top portion can be easily processed to have concavities and convexities.

Furthermore, the resist film may be patterned after forming irregularities on the surface of the resist film on which the pattern 3 is to be formed.

In the basic process of the present invention illustrated in this example, the photomask pattern and drawing pattern data for forming pattern 3 are usually the same as the layout pattern when manufacturing a semiconductor circuit, so the pattern is converted and manufactured. This eliminates the need for a process to simplify the process. In addition, since the exposure and development conditions when forming this pattern with resist etc. are the same as in the conventional method, there is no need to re-optimize for a wide pattern, and a sufficient margin for practical use can be expected.

〔Effect of the invention〕

As explained above, according to the pattern forming method of the present invention, any opening pattern including extremely fine openings, which was difficult to realize using conventional techniques, can be easily and precisely formed in a film of any thickness. Therefore, it has a remarkable effect in manufacturing semiconductor devices and the like.

[Brief explanation of the drawing]

Figures 1 a to d are diagrams showing the basic steps and steps of the example of the pattern forming method of the present invention, and Figures 2 a to d
e is a diagram showing another basic step and the steps of an embodiment of the pattern forming method of the present invention, FIGS. 3 a to e are process diagrams of another embodiment of the present invention, FIGS. 4 a to d, and FIG. 5 A to C are process diagrams of a conventional pattern forming method, respectively. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Adhesive film, 2', 2''...Fragile parts of the adhesion film, 3...Pattern made of material such as resist, 4...Opening formed in the same pattern,
5...Opening formed in the attached film.

Claims (1)

[Scope of Claims] 1. One micropattern with a substantially bell-shaped cross-section on a substrate, or an aggregate of a plurality of adjacent micropatterns arranged such that their bottoms are substantially in contact with each other and their tops have a gap. a first step of forming at least one of the patterns; a second step of depositing a film thicker than the pattern over at least the pattern and the substrate by a directional film deposition method; and a second step of depositing a film thicker than the pattern over at least the pattern and the substrate, and etching. a third step of removing a portion of the film in contact with the surface of the pattern, and forming a predetermined opening pattern in the film. 2 In the first step, first, a film made of a first material is formed on the substrate, and then at least one of the minute pattern or aggregate pattern made of a second material is formed, and then the pattern is masked. 2. The pattern forming method according to claim 1, further comprising the step of selectively removing said first material film. 3. The pattern forming method according to claim 1, wherein the directional film deposition method is an ECR plasma deposition method. 4. A first step of forming a pattern having unevenness at least on the top of the substrate, and depositing a film thicker than the pattern over at least the pattern and the substrate by a directional film deposition method. A pattern forming method comprising: a second step; and a third step of removing a portion of the film in contact with the surface of the pattern by etching, to form a predetermined opening pattern in the film. 5. The pattern forming method according to claim 4, wherein in the first step, the unevenness of the pattern is formed by exposure and development processing. 6. The pattern forming method according to claim 4, wherein in the first step, the unevenness of the pattern is formed by surface treatment using gas plasma.