JPH07123104B2 - Pattern formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pattern forming method for easily and highly accurately forming a fine resist pattern in a fine processing technique.

[Conventional technology]

FIG. 2 is a sectional view showing an example of a conventional pattern forming method. In FIG. 2, (1) is a substrate, (2) is a photoresist layer, (3) is an i-line with a wavelength of 365 nm, (4) is a mask,
(5) is heat treatment with a hot plate, (2a) and (2
b) is the first exposed portion and the first unexposed portion formed by the first exposure with the i-line (3) having a wavelength of 365 nm, (2c) is the processing (5) by the hot plate after the first exposure The formed altered portion, (2d), shows the second exposed portion formed by the second exposure of the entire surface of the resist layer with the i-line (3) having a wavelength of 365 nm.

Next, the pattern forming process will be described.

First, a photoresist which is sensitive to i-line (3) with a wavelength of 365 nm is spin-coated on the substrate (1) to form a photoresist layer (2).
To form. (FIG. 2A) Next, by using a mask (4), a partial region of the photoresist layer (2) is selectively subjected to a first irradiation with an i-line (3) having a wavelength of 365 nm.
Exposure is performed to form the first exposed portion (2a), and the unexposed portion is referred to as the first unexposed portion (2b) (FIG. 2B).

The entire wafer shown in FIG. 2B is subjected to heat treatment (5) with a hot plate in an amine-based catalyst atmosphere to form an altered portion (2c) (FIG. 2C).

Then, the second by the i-line (3) with a predetermined intensity of wavelength 365nm
When exposure is performed on the entire wafer shown in FIG. 2C, the first unexposed portion (2b) is exposed and becomes the second exposed portion (2d), but the altered portion (2c) is exposed by the first exposure. Since it has already been exposed, this step does not change (FIG. 2D).

Further, by developing with an alkaline developer, the second exposed portion (2d) is selectively removed, and the altered portion (2c) is left as a pattern on the substrate (1). (FIG. 2E) Here, the cross-sectional shape of the pattern formed by the conventional pattern forming method is an inverted trapezoid as shown in FIG. 2E. 2 and 3 show the principle of forming an inverted trapezoidal pattern by the conventional pattern forming method.

In FIG. 3, (A) shows the exposure intensity distribution of the photoresist layer (2) in the first exposure step shown in FIG. 2B, and similarly (B) shows the second exposure shown in FIG. 2D. The exposure intensity distribution in the process is shown. Further, the horizontal axis x represents the coordinates on the photoresist, and the vertical axis I represents the exposure intensity distribution.

(C) shows a change in the pattern shape in the developing step shown in FIG. 2E, and shows changes in the pattern shape over time in the order of (i), (ii), and (iii).
It is sectional drawing which showed the process in which the exposure part (2d) is selectively melted and removed.

(D), (E), and (F) are diagrams showing changes in the photosensitizer in the photoresist in the pattern forming step. (D) is a diazoketone derivative, (E) is a carboxylic acid derivative, and (F) is an indene derivative. It is a figure.

In the first exposure step shown in FIG. 2B, when the first exposure is performed through the mask (4), the exposure intensity distribution in the photoresist (2) is affected by a diffraction phenomenon or the like, and the exposure intensity distribution in FIG. The exposure intensity distribution is as shown in FIG. Further, the diazoketone derivative (I) which is a photosensitizer in the photoresist (2) is
It decomposes to a carboxylic acid derivative (J), and the decomposition amount increases as the exposure amount increases. Therefore, if the first exposure is performed with the exposure intensity shown in FIG. 3 (A) for a certain period of time, the exposure amount increases according to the magnitude of the exposure intensity. This is sufficient, and the amount of decomposition of the photosensitizer in the photoresist (2) becomes small, and the shape of the first exposed portion (2a) becomes as shown in FIG. 2B.

Next, in the thermomechanical treatment step using the hot plate shown in FIG. 2C, only the carboxylic acid derivative (J) in the first exposed portion (2a) chemically reacts to become the indene derivative (K) and the altered portion (2c). While the diazoketone derivative (I) in the first unexposed portion (2b) remains unchanged.

Further, in the second exposure step shown in FIG. 2D, the undecomposed diazoketone derivative (I) in the first exposure step is decomposed,
It becomes the carboxylic acid derivative (J) and forms the second exposed portion.
In the second exposure, since the exposure is performed for a certain period of time with the exposure intensity shown in FIG. 3 (B), the exposure amount is constant over the entire surface of the photoresist. Therefore, the first unexposed portion (2b) becomes the second exposed portion (2d).

Next, in the developing step shown in FIG. 2E, the carboxylic acid derivative (J) is easily soluble in the developing solution, the indene derivative is poorly soluble in the developing solution, and the carboxylic acid derivative (J) is contained in a large amount. The exposed part (2d) is selectively removed, and the altered part (2c) containing a large amount of the indene derivative (K) is left on the substrate (1). FIG. 3 (c) shows the process of development with the lapse of time. Since the difference in dissolution rate between the altered portion (2c) and the second exposed portion (2d) during development is sufficiently large, the second exposed portion (2d)
The second exposed portion (2d) is removed in the order of (i), (ii), and (iii), and when the development is completed, the altered portion (2c) is left on the substrate (1). The inverted trapezoidal pattern shown in FIG. 2E is formed.

[Problems to be Solved by the Invention]

The cross-sectional shape of the pattern obtained by the conventional pattern forming method is an inverted trapezoid. The resist pattern is mainly used as an etching mask, but if the cross-sectional shape of the pattern is an inverted trapezoid, there is a problem that etching cannot be performed faithfully to the pattern.

The present invention has been made to solve the above-mentioned problems, and when a resist pattern is used as a mask for etching, a resist having a rectangular cross-section capable of performing etching faithfully to the resist pattern is used. The purpose is to form a pattern.

[Means for Solving the Problems]

A pattern forming method according to the present invention is a resist containing a material sensitive to light, radiation or particle beams in a first energy region and a second energy region, and a material absorbing light, radiation or particle beams in a second energy region. Is used to selectively perform the first irradiation in the first energy range, the resist layer after the first irradiation is heat-treated to change into a negative resist, and the second irradiation in the second energy range is used to perform the first irradiation. The area near the surface of the resist except the exposed portion is made easily soluble in the developing solution, and the area near the interface between the resist and the substrate is made slightly soluble in the developing solution, and then developed to form a pattern. It is a thing.

[Action]

The pattern forming method according to the present invention uses the second resist
Since the material that is sensitive to light, radiation or particle beams in the energy range and the material that absorbs the light, radiation or particle beams are included, light and radiation in the second energy range near the surface of the resist in the second irradiation step. Or, the particle beam is absorbed and, as a result, the second beam near the interface between the resist and the substrate is absorbed.
The amount of light, radiation or particle beam in the energy range is reduced.

As a result, the dissolution rate in the developing solution near the surface of the resist becomes high and the dissolution rate in the developing solution near the interface between the resist and the substrate becomes low, so that the cross-sectional shape of the pattern can be made rectangular.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Note that the same or corresponding parts as those of the conventional one are designated by the same reference numerals and the description thereof will be omitted. FIG. 1 is a sectional view showing an embodiment of a pattern forming method according to an embodiment of the present invention. In FIG. 1, (6) is a photoresist containing a dye that absorbs g-line of 436 nm wavelength, (7) is g-line of 436 nm wavelength, (6a) and (6).
b) is the first exposed portion and the first unexposed portion formed by the first exposure with the i-line (3) having a wavelength of 365 nm, and (6c) is the altered portion formed by the heat treatment (5) with the hot plate. , (6
d) shows the second exposed portion formed by the second exposure of the entire surface of the photoresist layer with the i-line (7) having a wavelength of 436 nm.

Next, the pattern forming process will be described.

First, on a substrate (1), a photoresist that is exposed to an i-line (3) of 365 nm wavelength and a g-line (7) of 436 nm wavelength
A photoresist added with a dye that absorbs 36 nm g-line is spin-coated to form a photoresist layer (6).

(FIG. 1A) Next, by using the mask (4), a partial region of the photoresist layer (6) is selectively subjected to the first irradiation with the i-line (3) having a wavelength of 365 nm.
Exposure is performed to form a first exposed portion (6a), and the unexposed portion is referred to as a first unexposed portion (6b). (FIG. 1B) The entire wafer shown in FIG. 1B is heated (5) by a hot plate in an amine-based catalyst atmosphere to transform the altered portion (6c).
To form. (Fig. 1C) Then, the second line by the g-line (7) with a predetermined intensity of wavelength 436 nm
When exposure is performed on the entire wafer shown in FIG. 1C, the first unexposed portion (6b) is exposed and becomes the second exposed portion (6d), but the altered portion (6c) has already been exposed by the first exposure. Therefore, it is not changed by this process. (FIG. 1D) Further, by developing with an alkaline developer, the second exposed portion (6d) is selectively removed, and the altered portion (6c) is left as a pattern on the substrate (1). (FIG. 1E) Here, the cross-sectional shape of the pattern formed by the pattern forming method according to the present invention is rectangular as shown in FIG. 1E. The principle of forming a rectangular pattern in one embodiment of the present invention will be described with reference to FIGS. 1, 3, and 4.

FIG. 4 shows changes in the pattern shape in the developing step, in the order of (i), (ii), (iii) with the passage of time.
It is a cross-sectional view showing a change in the pattern shape and showing a process in which the second exposed portion (6d) and a part of the altered portion (6c) are removed.

In the coating process shown in Fig. 1A, g-line with wavelength of 436 nm (7)
Although a photoresist that absorbs light is applied, in the first exposure step shown in FIG. 2B, since the exposure is performed using the i-line (3) with a wavelength of 365 nm, the same principle as in the first exposure step by the conventional method is used. According to the principle, the shape of the first exposure part (6a) is as shown in FIG. 1B.

Further, in the heat treatment step using the hot plate shown in FIG. 1C, the dye that absorbs the g-line having a wavelength of 436 nm is stable and does not change with respect to the heat treatment. Alteration part (2c)
Based on the same principle of formation, the shape of the altered part (6c) is the first
It becomes as shown in FIG.

Next, in the second exposure step shown in FIG.
The second exposure is performed on the entire surface of the photoresist layer shown in Fig. 3 by g-line of wavelength 436 nm, which is different from the conventional method. However, since the photoresist layer contains a dye that absorbs g-line of wavelength 436 nm, it is shown in Fig. 3 ( When exposed for a predetermined time with the exposure intensity shown in B), the exposure amount is large near the surface of the photoresist layer and small near the interface between the photoresist layer and the substrate (1). Therefore, a large amount of the carboxylic acid derivative (J) is produced near the surface of the second exposed portion (6d), but the amount of decomposition of the diazoketone derivative (I) is reduced near the interface between the photoresist layer and the substrate (1), and the diazoketone derivative (I) is reduced. The derivative (I) remains. Moreover, since the altered portion (6c) has already been exposed, it does not change.

Then, in the developing step shown in FIG. 1E, the diazoketone derivative (I) and the indene derivative (K) are sparingly soluble and the carboxylic acid derivative (J) is easily soluble in the developing solution. Therefore, near the surface of the second exposed portion (6d), the carboxylic acid derivative (J) that is easily soluble in the developer is large and the dissolution rate is high, but near the interface of the substrate (1), the diazoketone derivative that is sparingly soluble in the developer is However, the dissolution rate decreases.

Further, the altered portion (6c) contains a large amount of a sparingly soluble indene derivative (K) in the developing solution, but gradually dissolves. FIG. 4 shows the developing process over time. During development, the difference in dissolution rate between the surface of the altered portion (6c) and the second exposed portion (6d) is sufficiently large, but the substrate (1) of the altered portion (6c) and the second exposed portion (6d) Since the difference in dissolution rate near the interface is not large enough, the altered part (6c) is also partially removed, (i),
In order of (ii) and (iii), the second exposure part (6d) and the alteration part (6
Part of c) is removed, part of the altered part (6c) is left on the substrate (1), and the rectangular pattern shown in FIG. 1E is formed.

In the above example, a photoresist containing a dye that absorbs g-rays having a wavelength of 436 nm was used, and the wavelength of 436 n was used during the second exposure.
Although the pattern forming method of exposing the entire surface of the photoresist layer by the g line of m is shown, the photoresist used in the conventional pattern forming method has a large absorption in the far-ultraviolet light region. By using far-ultraviolet light, for example, ultraviolet light having a wavelength of 254 nm, the same effect as that of the above-described embodiment can be obtained.

〔The invention's effect〕

As described above, the pattern forming method according to the present invention is
In the first irradiation step and the second irradiation step, irradiation with light, radiation or particle beams in different energy ranges is performed, and a resist containing a material that selectively absorbs light, radiation or particle beams in the second energy range is used. As a result, the cross-sectional shape of the resist pattern can be made rectangular, and by using this resist pattern as a mask during etching, it is possible to perform etching faithfully to the pattern.

[Brief description of drawings]

1 (A) to (E) are sectional views showing a pattern forming method according to an embodiment of the present invention, and FIGS. 2 (A) to (E).
Is a cross-sectional view showing a conventional pattern forming method, FIG. 3 (A) is a view showing an exposure intensity distribution in a photoresist layer at the time of the first exposure, and FIG. 3 (B) is an exposure of the photoresist layer at the time of the second exposure. A diagram showing the intensity distribution, FIG. 3 (C),
FIG. 3D is a cross-sectional view showing the shape change of the resist pattern in the developing step in the conventional pattern forming method in the order of (i), (ii), and (iii) with the lapse of time. Fig. 3 is a diagram showing a structural formula, Fig. 3 (E) is a diagram showing a structural formula of a carboxylic acid derivative, Fig. 3 (F) is a diagram showing a structural formula of an indene derivative, and Fig. 4 is a pattern in the present invention. It is the figure which showed the shape change of the resist pattern in the image development process in a formation method in order of (i), (ii), (iii) with progress of time. In the figure, (1) is a substrate, (2) is a photoresist,
(2a) is the first exposed part, (2b) is the first unexposed part, (2c) is the altered part, (2d) is the second exposed part, and (3) is the i of wavelength 365 nm.
Line, (4) mask, (5) heat treatment with hot plate, (6) photoresist containing dye that absorbs g-line of 436 nm wavelength, (6a) first exposed portion, (6b) first unexposed part Exposure part, (6c) altered part, (6d) second exposure part, (7) g line of wavelength 436 nm, (x) coordinates, (I) exposure intensity,
(I) is the pattern shape after a second, (ii) is the pattern shape after b seconds, (iii) is the pattern shape after c seconds, and is a second,
It indicates that time elapses in the order of b seconds and c seconds.

Claims (1)

[Claims] 1. A material sensitive to light, radiation or particle beams in a first energy region and a second energy region different from the first energy region on a substrate and light, radiation or particle beams in the second energy region. Forming a resist layer by applying a resist containing a material that absorbs light, and selectively irradiating a partial region of the resist layer with light, radiation or particle beams in the first energy range. And a step of heat-treating the resist layer after the first irradiation to change the first-irradiated portion into a negative type resist, and a step of performing the heat treatment by light, radiation or particle beam in the second energy range. A second irradiation is performed on the entire substrate to make the vicinity of the surface of the resist in the region excluding the first irradiated portion easily soluble in the developing solution, and the interface between the resist and the substrate. A step of around a hardly soluble in the developer, and then development is performed, a pattern forming method which comprises a step of forming a pattern.