JPH02127645A - Formation of positive type pattern - Google Patents

Abstract

PURPOSE:To surely form fine positive type patterns by applying a specific pattern forming material on a substrate surface, irradiating the coating with light having 1st and 2nd wavelengths and acting a silylating agent on the surface of the pattern forming material. CONSTITUTION:The pattern forming material (resist) 2 is prepd. by dissolving a novolak resin and 1.2-naphthoquinone diazide-5-sulfonyl chloride in ethoxyethyl acetate which is a solvent. Only the desired parts of the resist 2 surface formed on the substrate 1 surface are irradiated with UV rays 5 and are thereby exposed. Silylation accelerating regions 35 are thereafter formed. The entire part of the resist 2 is irradiated with mercury bright lines as light 51 to put the regions which are not exposed in the previous stage into the state of allowing the easy silylation. The silylation reaction on the surface of the resist 2 is effected in the stage of forming the silylated regions 36. Etching is thereafter executed by O2 plasma 7, by which the formation of the fine patterns is executed.

Description

[Detailed Description of the Invention] [Summary] Regarding the method of forming a pattern using a positive photosensitive resist, the purpose of this invention is to form an extremely fine positive pattern more accurately and reliably than before, using an aromatic ring structure having a phenolic hydroxyl group. By irradiating the resin containing in the molecule with light having the first wavelength,
a step of applying a pattern forming material on the substrate surface comprising a compound that suppresses silylation and promotes silylation by irradiating light having a second wavelength longer than the first wavelength; a step of exposing a pattern to be formed on the forming material using light having the first wavelength; a step of irradiating the surface of the pattern forming material with light having the second wavelength; and a step of irradiating the pattern forming material with light having the second wavelength. The method includes a step of applying a silylating agent to the surface, and a step of etching away the surface of the pattern forming material by dry etching using plasma containing oxygen atoms.

[Industrial application field]

The present invention relates to a method for forming a pattern using a positive photosensitive resist. Specifically, by using a novolac photosensitive resist with high sensitivity to ultraviolet light with a wavelength of 300 nm or less and high resolution, and dry etching after selective silylation treatment, a fine positive pattern can be created. It relates to a method for accurately forming a .

In the manufacturing process of semiconductor integrated circuits, a resist is formed on the surface of a semiconductor substrate to be processed using a photolithography method, and then this resist itself is used as a mask to perform processes such as dry etching and ion implantation. . For this purpose, the material of the resist must have sufficient resistance as a mask and must be able to form a pattern accurately.

BACKGROUND ART In recent years, as semiconductor integrated circuits have become more highly integrated and densely packed, there has been a demand for pattern forming techniques that can make the components of integrated circuits smaller and more accurate.

[Prior Art] In addition to good sensitivity to light, the conditions for so-called photosensitive resists, in which a desired portion of a photosensitive material coated on the surface of a substrate is irradiated with light and the desired portion is left as a mask, include: It is important that the resolution is good.

In recent pattern development, the use of dry etching, which is suitable for forming fine patterns, is being considered. In order to obtain a pattern with good resolution in dry etching development processing, it is necessary to use a material that has good resistance to dry etching in the areas that should be left during etching6 and has significant brittleness in the areas that should be removed. Must be selected as a resist material. As a material that does not meet the above conditions, for example, the active hydrogen of a novolac resin can be replaced with a functional 5 (-5i-(C
Ih)3. There is a so-called "selective silylation method" in which the silylation is carried out by substituting the silylation group with a monoclonal group. Details of this method can be found, for example, in 5PIE (The 5ociety of Pho
to-Optical lnstrumentat4o
n Engineers) Vol, 631 Adv
ances 1nResist Technology
and processing III (19
86) pp. 34-39.

However, even with this method, the i-line of the mercury emission line (wavelength 3
Although it is sensitive to ultraviolet rays with relatively long wavelengths such as 65 nm) and G-line (wavelength 436 nm), it has not been possible to obtain one that is sensitive to ultraviolet rays with a wavelength of 3Q Onm or less, which has been in strong demand recently. Therefore, the goal is to develop a resist for selective silylation that is sensitive to ultraviolet light having a wavelength of 300 nm or less.

Very recently, as a resist material, a silylated resist that can form a positive pattern has been realized using a mixture of novolac resin and a material sensitive to ultraviolet light with a wavelength of 300 nm or less, such as an ultraviolet excimer laser (patent application filed in 1983).
-302462 invention) has appeared. This method will be explained along the steps with reference to FIG. 2, which shows a cross section of the substrate. In FIG. 2, ■ is a substrate, which is a workpiece. 2 is a resist (pattern forming material). 3 is the exposure area;
This is the portion of the resist 2 that is exposed to the ultraviolet rays 5.

36 is a silylated region, which is a portion of the resist 2 that has undergone silylation. Reference numeral 4 denotes a mask, which blocks the irradiation of the purple rays 5 during exposure. 5 is ultraviolet light, 300n
It has a wavelength of less than m. 6 is a silylating agent. 7 is 0
□(Oxygen) plasma, used for etching. In addition, (a) is a step of applying resist 2 to the surface of substrate 1, and (b)
) is the pattern to be formed on resist 2 with a wavelength of 300
(c) is a step in which a silylating agent 6 is applied to the surface of the substrate 1; (d) is a step in which the surface of the substrate 1 is etched away by dry etching.

In this method, a pattern forming material 2 coated on the surface of a substrate 1 is used.
Mask 4 is used to cover only the desired part of the surface, and the wavelength is 300.
When exposed using ultraviolet light of nm or less, for example, KrF (krypton fluoride) excimer laser, only the exposed portion becomes less susceptible to silylation. If, for example, HMDS (hexamethyldisilazane) is applied to the entire surface of the substrate 1 as the silylating agent 6, the substitution reaction (silylation reaction) will proceed selectively only in the areas that have not been exposed to light.
On the other hand, silylation in exposed areas is significantly suppressed. then 0
□If dry etching such as RIE (reactive ion etching) is performed, the progress of etching will be further suppressed in the unexposed areas where silylation has progressed, and only the exposed areas will be selectively etched. A resist for selective silylation, which is exposed to UV excimer laser such as KrF (krypton fluoride), has been completed.

[Problem that the invention sought to solve]

However, with silylated resists used for boat fishing, including the method of Japanese Patent Application No. 62-302462, the progress of the silylation reaction in areas that are easily silylated (unexposed areas) is insufficient. However, the selectivity of silylation between exposed and unexposed areas was not good.

Since the unexposed areas are not sufficiently easily silylated, the dry etching resistance of the unexposed areas is insufficient.

For this purpose, RF is applied between the electrodes in the chamber in order to speed up the etching process and make the pattern sides steeper.
When the lightning voltage is increased or the gas pressure is decreased, even the unexposed areas that should be left are etched into frost columns. In an attempt to avoid this, lowering the RF lightning voltage applied between the electrodes in the chamber or increasing the gas pressure not only slows down the etching process and affects productivity, but also makes it difficult to perform anisotropic etching. The tendency of the particles to proceed isotropically increases, and the side surfaces of the parts that are not exposed to the ultraviolet rays are also gouged out. Such gouges become an obstacle to the formation of fine patterns.

On the other hand, portions of the resist surface that should not be silylated are actually very thinly silylated. Therefore, after finishing the silylation reaction and before starting the dry etching process, an additional process is added in which the entire surface of the resist is thinly etched to remove the silylated parts of the surface that should not be silylated. This process is called a light ashing process.However, since the light ashing process is usually performed on the entire resist surface, the surface of the mask portion that can be silylated is also removed at the same time.As a result, The silylated areas of the mask portion become thinner.

This results in a decrease in the dry etching resistance of the mask portion.

In the end, in the conventional selective silylation method, even if the etching conditions were changed or a light ashing step was added, there was a limit to the ability to accurately form extremely fine patterns.

The present invention was made in order to eliminate such drawbacks of the prior art, and aims to form an extremely fine positive pattern more accurately and reliably than in the past.

[Means to solve the problem]

In order to solve the problems of the prior art described above, the present invention has been developed by irradiating a resin containing an aromatic ring structure having a phenolic hydroxyl group in its molecule with light having a first wavelength. , suppresses silylation, and suppresses the first
A step of applying a pattern forming material consisting of a compound that promotes silylation to the substrate surface by irradiating light having a second wavelength longer than the wavelength of the pattern forming material, and forming a pattern on the pattern forming material. exposing the surface of the pattern-forming material with light having a first wavelength;
a step of irradiating light having the second wavelength; a step of causing a silylation agent to act on the surface of the pattern-forming material; and etching away the surface of the pattern-forming material by dry etching using plasma containing oxygen atoms. It has a step of doing as a means.

[Effect]

The present inventor newly obtained the following knowledge while further carrying out the research that led to the invention of Japanese Patent Application No. 62-302462.

Specifically, in an experiment on the silylation reaction of a novolak-based photosensitive resist, 1) when a resist containing a novolak resin and 1,2-naphthoquinonediazide sulfonyl chloride was irradiated with ultraviolet rays (i-rays) with a wavelength of 365r+m, silylation occurred even before irradiation. This will promote the development of

2) Project a KrF (krypton fluoride) excimer laser with a wavelength of 248 nm onto the part where silylation has been suppressed.
Even if irradiated with ultraviolet rays (i-rays) with a wavelength of 365 nm, this i-ray
There should be no difference in the degree of progress of silylation compared to before radiation irradiation.

As a result of intensive research based on the above knowledge, we have arrived at the present invention.

As described in the [Operation] section of the specification of Japanese Patent Application No. 62-302462, regarding the silylation suppression mechanism of a resist mixture containing a novolac resin and 1,2-quinonediazide sulfonyl halide by ultraviolet excimer laser light. is still not well understood. Similarly, wavelength 35
Light of 0 nm or more, for example, the i-line of the mercury emission line (365r+m
) is still not well understood.

According to the positive pattern forming process of the present invention, the unexposed areas that were masked during exposure by the pattern forming method of Japanese Patent Application No. 62-302462 shown as a conventional example are irradiated with light having a wavelength of 350 nm or more. - The layer becomes more susceptible to silylation. The portions that must be left in the etching process are more silylated, resulting in improved resistance to dry etching. Therefore, even under more severe etching conditions, such as increasing the RF lightning voltage applied between the electrodes, the problem that portions that should not be etched become frost pillar-like does not occur. Since the etching conditions can be made stricter, the sides of the resist can be made steeper, and a pattern with a higher aspect ratio can be obtained more quickly.

On the other hand, the silylated region is sufficiently deeply silylated compared to the portion that should not be silylated. Therefore, there is no need to add a light ashing process before the dry etching process.

Furthermore, according to the knowledge obtained by the inventors already mentioned in the [Operation] section, even if the part that has been treated to suppress silylation is irradiated with light 51 such as ultraviolet rays (i-rays) with a wavelength of 365 nm, silylation does not proceed. Since there is no change in the degree, there is no need to limit the irradiation of the light 51 to the θ■ region that was not exposed in the previous process, and therefore the light 51 can be irradiated over the entire surface, and a mask is not required in the process of irradiating the light 51. The process becomes easier.

〔Example〕

Embodiments of the present invention for more accurately forming a positive resist pattern sensitive to short wavelength ultraviolet rays will be described below with reference to FIG.

FIG. 1 is a process explanatory diagram of a pattern forming method according to an embodiment of the present invention. In the figure, the same numbers as in FIG. 2 indicate the same parts as in FIG. 2. In addition, 5 is ultraviolet light having a wavelength of 300 nm or less. 51 is light,
It has a wavelength of 350 nm or more.

In addition, (a) is a step of applying resist 2 to the surface of substrate 1,
(b) shows the pattern to be formed on resist 2 with a wavelength of 3
Step of exposing using ultraviolet rays 5 of 00 nm or less, (C)
(d) is a step in which a silylating agent 6 is applied to the surface of the substrate 1; (e) is a step in which the surface of the substrate 1 is etched away by dry etching. It is a process.

See Figure 1(a).

First, a pattern forming material (resist) 2 is formed on the surface of a substrate 1 to be processed. The substrate 1 is a semiconductor substrate with a diameter of 10 cm made of silicon with a plane orientation of (100), and the pattern forming material 2 includes 100 parts by weight of novolac resin 1.2-
It was prepared by dissolving 20 parts by weight of naphthoquinone cyato-5-sulfonyl chloride in 260 parts by weight of ethoxyethyl acetate as a solvent.

This pattern-forming material was coated onto the surface of the St (silicon) substrate 1 using a spinner at 4000 revolutions/min, and then heated at 100 °C in a dry nitrogen gas atmosphere.
After baking for seconds, a resist 2 having a thickness of 12,000 was formed. In this example, a stylus-type step measuring device was used to measure the film thickness of the resist 2.

See Figure 1(b).

Next, only a desired portion of the surface of the resist 2 formed on the surface of the substrate 1 is irradiated with ultraviolet rays 5 for exposure. For this purpose, using a mask 4, KrF (krypton fluoride) excimer laser light (248 nm) is irradiated under the condition of 150 mJ/cm'' (see FIG. 1(c)).

After this, the silylation promoting region 35 is formed. resist 2
The i-line (365 nm) of the mercury bright line is illuminated as light 51 on the entire surface.
00 to 300 mJ/cm'' to make the area not exposed in the previous step easily silylated.

See Figure 1(d).

This completes the exposure of the resist 2, and then moves on to the step of forming the silylated region 36. In this step, the surface of the resist 2 is silylated, that is, the hydrogen atom of -011 (hydroxyl group) is replaced with -5i-(CH3)*. For the silylation treatment, a method was adopted in which HMDS (hexamethyldisilazane) vapor was applied to the entire resist 2. The container 8 containing the silylating agent 6 and the surface of the resist 2 to be processed are stored in a container with a lid so that they do not come into direct contact with each other, and the container is heated at 140°C in a constant temperature bath for 4 hours.
Heat for 0 minutes.

As a result of this process, the depth from the surface of the silylated region 36 is approximately 2,000 to 3,000, which is 50,000 to 50,000 mm deep compared to that of the method of Japanese Patent Application No. 62-302462, which was adopted as a conventional method.
It became clear that silylation was progressing sufficiently compared to the case of 0.

Note that in this step (d), the vicinity of the surface of the silylation-inhibited region is also slightly more likely to be silylated, so if a light ashing step, that is, a step of very thin dry etching, is added after step (d), It's more effective. However, in the case of the present invention, the dry etching resistance of the masked portion is improved, and there is a sufficient difference in the susceptibility to etching between the masked portion and the non-masked portion, so that no additional light ashing step is required.

See Figure 1(e).

After this, etching with 0□ (oxygen) plasma 7,
0□ (oxygen) gas flow rate 60sec, pressure 0.02T
.

rr, and the power density was 3.0 W/cm'' for 2 minutes.

It was confirmed that the power density could be increased to IOW/cm''.

Through the above steps, the fine pattern processing using a positive resist, which is the object of the present invention, is completed. In this method, the silylation of portions that should not be etched progresses more than before, so that the etching selectivity is improved. As a result of using the method of the present invention, it was possible to obtain a nearly vertical pattern with a line and space of 0.5 μm without forming a frost column shape.

By the way, in the above example, novolak resin and 1,2-naphthoquinonediazide-5-sulfonyl chloride were used as the positive photosensitive pattern forming material.
CI (chlorine) may be replaced with X (halogen) by changing the substituent -5O□C1 attached to the aromatic ring to ~SO□X.

In addition to the semiconductor substrate used in this embodiment, the substrate 1 may be any substrate such as a glass substrate for a mask or a garnet substrate for a bubble memory. Furthermore, ultraviolet lf used for exposure! 5, the wavelength may be 300 nm or less, and KrF
(Krypton fluoride) Ar instead of excimer laser light
F (argon fluoride) excimer laser, synchrotron radiation (SOR) light, etc. can also be used.

〔Effect of the invention〕

According to the present invention, extremely fine patterning can be performed more accurately and reliably than in the past, so that ultra-fine patterning of semiconductor integrated circuits and the like can be achieved with a high yield.

[Brief explanation of drawings]

The attached drawings are all cross-sectional views. FIG. 1 is a process diagram of a pattern forming method according to an embodiment of the present invention, and FIG. 2 is a process diagram of a conventional pattern forming method. In the figure, 1...substrate, 2...resist, 3...exposure area,
35...Silylation promotion region, 36...Silylation region, 4...Mask. 5... Light having a first wavelength (ultraviolet light with a wavelength of 300 nm or less), 51... Light having a second wavelength (light with a wavelength of 350 r+m or less), 6... Silylating agent, 7・
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Claims (4)

[Claims] (1) Silylation is suppressed by irradiating a resin containing an aromatic ring structure having a phenolic hydroxyl group in its molecule with light having a first wavelength, and a second wavelength longer than the first wavelength. A step of applying a pattern forming material (2) comprising a compound that promotes silylation onto the surface of the substrate (1) by irradiating light having a a step of exposing using light (5) having the first wavelength; a step of irradiating the surface of the pattern forming material (2) with light (51) having the second wavelength; and a step of exposing the surface of the pattern forming material (2) with the light (51) having the second wavelength; (2) A process of applying a silylating agent (6) to the surface of the pattern forming material (2), and etching away the surface of the pattern forming material (2) by dry etching using plasma containing oxygen atoms. Formation method. (2) The compound contained in the pattern forming material (2) has an aromatic ring structure in the molecule that has a substituent represented by the general formula -SO_2X (where X is a halogen group) and does not have a phenolic hydroxyl group. 2. The method for forming a positive pattern according to claim 1, wherein a compound comprising: (3) Compounds contained in the pattern forming material (2) include 1,2-naphthoquinonediazide-4-sulfonyl halide, 1,2-naphthoquinonediazide-5-sulfonyl halide, and 1,2-benzoquinonediazide-4-sulfonyl halide. 2. The method for forming a positive pattern according to claim 1, wherein a compound selected from the group consisting of , anthraquinonediazide sulfonyl halide, and phenanthrenequinonediazide sulfonyl halide is used. (4) Select a wavelength of 300 nm or less as the first wavelength,
4. The method of forming a positive pattern according to claim 1, wherein a wavelength of 350 nm or more is selected as the second wavelength.