JPH032759A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To improve the resist profile of an acid generating chemical amplification type resist and to extend the focus margin by treating the resist with an acid trapping agent before or after exposure. CONSTITUTION:A semiconductor substrate 10 is coated with a negative type acid generating chemical amplification type resist 11 and this resist 11 is exposed through a photomask to form an exposed part 11A. The surface of the resist 11 is then treated with imidazole as an acid trapping agent. By this treatment, the concn. of the acid in the surface layer of the resist film 11 is made relatively lower than that in the lower part. A resist shape having perpendicular profile corresponding to the concn. distribution of the acid is obtd., the resolution of the resist is improved and the focus margin is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a resist pattern used in lithography technology, and more particularly to an acid-generating chemically amplified resist.

[Summary of the Invention] The present invention provides a method for forming a resist pattern using an acid-generating chemically amplified resist, by treating with an acid trapping agent before or after exposure, or by creating a temperature gradient in the resist film thickness direction after exposure. By performing baking with a high temperature, the pattern shape of the resist is improved and the focus margin is expanded.

[Prior Art] For example, resists used in photolithography technology for semiconductor devices are described in the monthly publication Sem1conducto.
r World I 988, 9 pages 44-46, 0-naphthoquinone diazide (NQ
D)/Novolac resin In addition to positive resist, poly(p-
Positive resists are known, which are made by adding an acid generator to a base polymer (trimethylsiloxystyrene). As shown in the formula below, when a positive resist containing this acid generator is irradiated with light in the presence of an acid generator, the silyl group is removed and becomes alkali-soluble poly(p-hydroxystyrene), which is then developed by alkali development. The exposed area is dissolved and a positive pattern is obtained.

Acid generator - acid (CH-C)(,)n (CH-CH2)n acid OSi CHs OHH3 Furthermore, in recent years, a resist having higher resolution than the above-mentioned resist has been called a chemically amplified resist. High-sensitivity resists are being developed.

This chemically amplified type resist is composed of a negative type resist that includes an alkali-soluble resin, a crosslinking agent, and a photosensitive acid-generating side, and a positive type resist that is composed of an alkali-soluble resin, a dissolution inhibitor (group), and a photosensitive acid-generating side. It is made up of additives. In a negative acid-generating character width type resist, the exposed area is cross-linked and insolubilized during post-exposure baking (FEB) using the acid generated by the photosensitive acid-generating side as a catalyst, and a negative pattern is obtained by alkaline development. . On the other hand, in the case of a positive acid-generating chemically amplified resist, the dissolution inhibitor (base) is decomposed in the exposed area using the generated acid as a catalyst and becomes alkali-soluble, thereby obtaining a positive pattern.

Note that FIGS. 8 to 9 show a pattern forming method using the above-described negative acid-generating chemically amplified resist.

First, as shown in FIG. 9A, an acid-generating chemically amplified resist 2 is applied onto a semiconductor substrate 1, and then exposed to light. The light intensity profile on the surface of the resist 2 due to this exposure is as shown in FIG. 8, and the exposed portion 21 is formed as shown in FIG. 9B in accordance with this light intensity. Next, when a post-exposure bake (PER) is performed, an insolubilized portion 2b is formed as shown in FIG. 9C, and a pattern is formed by alkali development (FIG. 9D).

Moreover, FIGS. 10 to 11 show a pattern forming method using a positive acid-generating chemically amplified resist.

First, as shown in FIG. 11A, an acid-generating chemically amplified resist 2 is coated on a semiconductor substrate I, and then exposed to light to form an exposed portion 2a as shown in FIG. 1B. On this occasion,
The light intensity profile on the surface of the resist 2 is as shown in FIG. 1O. Next, baking (FEB) is performed to form a solubilized portion 2c, and further, alkaline development is performed to dissolve the solubilized portion 2c and form a pattern (FIG. 11D).
.

[Problems to be Solved by the Invention] However, in the resist pattern forming method using the above-mentioned negative acid-generating chemically amplified resist, the pattern profile is as shown in Figure 9 due to light absorption of the remaining resin. As shown in Figure 2, there is a problem that the pattern shape is reversely tapered, and with this pattern shape, it is impossible to measure the line width at the bottom of the resist, and it is difficult to introduce it into the actual semiconductor manufacturing process. ing.

In addition, for positive acid-generating chemically amplified resists,
Due to the light absorption of the resin, the pattern profile becomes
As shown in the figure, it has a tapered shape and has the problem of poor reproducibility.

The present invention was devised in view of these conventional problems, and is intended to improve the resist profile of an acid-generating chemically amplified resist and to expand the focus margin.

[Means for Solving the Problems] Accordingly, the present invention provides a method for forming a resist pattern using an acid-generating chemically amplified resist, in which treatment with an acid trapping agent is performed before or after exposure, or the resist film is treated with an acid trapping agent after exposure. The solution is to perform baking with a temperature gradient in the thickness direction.

[Function] In the invention described in claim 1, by performing treatment with an acid trapping agent after the exposure preamble, the acid concentration near the surface layer of the applied resist film after exposure is made relative to that in the lower part of the resist film. to lower the target. Therefore, in the subsequent heat treatment, the acid concentration near the boundary between the exposed and unexposed areas is suppressed to a concentration sufficient to crosslink and insolubilize the negative type, and as a result, the area near the boundary becomes solubilized. In the center of the exposure area,
Due to the strong light intensity, the acid concentration is not high enough to solubilize. Therefore, a resist shape with a vertical profile corresponding to the acid concentration distribution is obtained, and the resolution and focus margin are expanded. On the other hand, in a positive acid-generating chemically amplified resist, the acid concentration near the boundary between the exposed and unexposed areas is suppressed to a level sufficient to be solubilized during subsequent heat treatment, and as a result, the acid concentration near the boundary is Becomes insoluble.

In the center of the unexposed region, no acid is generated and solubilization is not achieved.

In the second aspect of the invention, by creating a temperature gradient in the resist film thickness direction during baking after exposure, for example, in the case of a negative acid-generating chemically amplified resist,
By lowering the temperature of the resist film surface, it is possible to reduce the top line width of the pattern and make the pattern have a vertical profile. Furthermore, in the case of a Bot type acid-generating chemically amplified resist, lowering the temperature of the resist film surface increases the line width at the upper part of the pattern, making it possible to form the pattern into a vertical profile.

[Example] Hereinafter, details of the method for forming a resist pattern according to the present invention will be described based on an example shown in the drawings.

(First example) 1 to 2 show a first embodiment.

First, as shown in FIG. 2A, a negative acid-generating chemically amplified resist 11 is applied onto a semiconductor substrate 1O.

Note that this acid-generating chemically amplified resist is composed of a cresol-based resin, an acid generator that generates hydrogen halide upon irradiation with light, and a crosslinking agent.

Next, exposure is performed using a photomask (not shown) as a mask to form an exposed area +1A in the acid-generating chemically amplified resist 1 as shown in FIG. 2B.

Note that during exposure, the surface of the resist 11 has a light intensity profile as shown in FIG.

Next, the surface of the acid-generating chemically amplified resist 11 is treated with imidazole as an acid trapping agent. Due to the treatment with the acid trapping agent, a large amount of the acid generated in the exposed portion 11A of the resist 11 due to exposure is captured by imidazole on the surface side of the resist 11, and the amount of captured acid gradually decreases from the surface toward the lower side. Furthermore, since the central portion of the exposed area 11A receives strong light as shown in the light intensity profile of FIG. 1, the acid concentration is sufficiently high and is not solubilized even after the acid trapping agent treatment. On the other hand, the exposure section 11a
Because the area near the boundary with the unexposed area receives weak light,
The concentration of acid generated is low, and it is solubilized by treatment with the acid trapping agent. In addition, in FIG. 2C, lla indicates an insolubilized portion and llb indicates a solubilized portion.

Next, baking treatment and alkaline development are performed to form a resist pattern in which the insolubilized portion 11a remains as shown in the second diagram, and then predetermined treatments such as rinsing liquid treatment and hard baking are performed. Pattern formation is completed.

In the first embodiment, the present invention was applied to a negative type acid-generating chemically amplified resist, but it is also possible to obtain a vertical pattern profile even when applied to a bottom type resist.

Further, the acid generator, acid trapping agent, crosslinking agent, and base polymer of the resist can be changed as appropriate. For example, as the acid trapping agent, an aqueous solution of weakly basic tertiary amines can be used. Note that the same effect can be obtained even if the acid trapping agent treatment is performed in the exposure section 7.

(Second example) Figures 3 and 4 show a second embodiment.

First, in this embodiment, a positive acid-generating chemically amplified resist 12 is coated on the semiconductor substrate 10 (FIG. 4A), and then,
Exposure is performed using a photomask (not shown) to form exposed portions 122L. The light intensity profile on the surface of the resist 12 in this case is as shown in FIG. 3, and therefore, the width of the exposed portion 12a decreases toward the bottom.

Next, the semiconductor substrate lO on which the resist 12 is arranged,
Baking is performed using a baking device as shown in FIGS. 5 and 6. This baking device is configured such that a heater 13 and a cooler 14 that cools the surface of the renost face each other. FIG. 6 is an enlarged view of the main parts of the Beta device,
A number of nozzles 14a are provided on the lower surface of the cooler 14 to discharge cooled nitrogen (N) gas. Therefore, as shown in FIG. 7, a temperature gradient occurs in the thickness direction of the resist 12, and the temperature increases from the resist surface toward the bottom of the resist.

In this way, the resist surface is cooled, so the insolubilization reaction is promoted, and the cooling is weakened in the lower part of the resist, so the insolubilization reaction is reduced. The solubilization reaction of the acid-generating chemically amplified resist depends on the acid-catalyzed reaction during baking, so the solubilization is suppressed in the cooled area, and the exposed area 12A is as shown in FIG. 4C. , are formed in the solubilized portion +2a and the insolubilized portion +2b.

Next, when alkali development is performed, only the solubilized portion 12a is dissolved, and a vertical pattern profile can be formed, as shown in the fourth diagram.

In the above embodiments, the present invention was applied to a case where a positive type acid-generating chemically amplified resist was used, but it is of course applicable to a case where a negative type resist is used. In this case, post-exposure baking (FE)
B) As the temperature increases, the crosslinking reaction is promoted and the sensitivity increases. For this reason, in the case of a negative type, a conventional process results in an inverted tapered shape, but during baking after exposure, cooling gas is blown onto the resist surface to lower the surface temperature and reduce the line width at the top of the resist, resulting in a vertical pattern. It becomes possible to obtain a profile.

In addition, in the above embodiment, the cooler 14 of the baking device
Although the nitrogen gas discharging means is used, other gases or other methods may be used for cooling.

Furthermore, it goes without saying that the exposure process may be performed using a baking device.

[Effects of the Invention] As is clear from the above explanation, according to the method for forming a Rennost pattern according to the present invention, a good pattern profile can be obtained even if the acid-generating chemically amplified resist is positive type or negative type. This has the effect of increasing the focus margin.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the light intensity profile on the resist surface of the first embodiment according to the present invention, FIG. 2 A to 2nd diagram are process diagrams of the first embodiment, and FIG. Waveform diagrams showing the light intensity profile of the resist surface, FIG. 4A~
The fourth diagram is a process diagram of the second embodiment, FIG. 5 is an explanatory diagram of the baking device, FIG. 6 is an enlarged view of the main parts of the baking device, and FIG. 7 is a graph showing the temperature gradient in the thickness direction of the resist. FIG. 8 shows a light intensity profile, and FIGS. 9A to 9A are process diagrams of a conventional example using a negative type acid-generating chemically amplified resist.
FIG. 1O is a waveform diagram showing a light intensity profile, and FIGS. 1F to 11A are process diagrams of a conventional example using a positive acid-generating chemically amplified resist. 11.1'2...Acid-generating chemically amplified resist. Figure 1 Figure 2 A (1st implementation test 1) Figure 2 B Intensity profile of L2 bump 11 Figure 3 Figure 4 B ()11 Hole Power straddle A row) Fig. 2 D (Second charge A row (Second History #: Break 1) Fig. 4 D (A, tJ Pi Itari) Fig. 9 D (I X Mi I Itari J) Fig. 11 Diagram D

Claims (2)

[Claims] (1) A method for forming a resist pattern using an acid-generating chemically amplified resist, which comprises performing treatment with an acid trapping agent before or after exposure. (2) A method for forming a resist pattern using an acid-generating chemically amplified resist, which comprises baking after exposure with a temperature gradient in the direction of the resist film thickness.