JPS61231549A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To make a vacuum deposition stage unnecessary and to remarkably simplify stages for forming a resist pattern by using the silyl ether of novolak as the material of the intermediate layer of a resist having a three-layered structure so that the three-layered film is formed by a single baking. CONSTITUTION:A lower layer 20 is formed by spin coating, an intermediate layer 22 made of the silyl ether of novolak is formed on the layer 20 by spin coating, and irradiated with ultraviolet rays having shorter wavelengths and an upper layer 23 is formed on the layer 22 by spin coating. Since the intermediate layer 22 is formed by spin coating, a vacuum deposition stage required to form an SiO2 layer is made unnecessary. The intermediate layer 22 is made insoluble in a solvent by irradiation with ultraviolet rays having shorter wavelengths, so most of resists can be spin-coated on the layer 22 to form the upper layer 23. A prebaking stage required sometimes to make the intermediate layer 22 insoluble before the formation of the upper layer 23 is made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of forming a fine resist pattern on the submicron order used in the manufacture of semiconductor devices.

(Prior Art) In recent years, demands for higher integration of semiconductor devices and the like have been increasing, and along with this, technical demands regarding the formation of fine patterns have also become increasingly strict. As a microfabrication technology that meets these demands, a resist pattern is formed using ionizing radiation such as electron beams, X-rays, and short-wavelength ultraviolet rays, and then the resist pattern is precisely formed by dry etching using ions, plasma, etc. There is a need for a method for transferring to an underlying layer such as a substrate.

By the way, as characteristics of the resist used in such microfabrication, high resolution, high sensitivity, and high dry etching resistance are naturally required. However, in the case of large-scale integrated circuits (LSI), the surfaces of wafers including substrates are often uneven, and patterning of a resist layer on such an uneven surface is difficult to avoid. Due to the influence of diffused reflection and interference of light caused by the resist pattern, the pattern dimensions are susceptible to changes, making it difficult to keep the resist pattern within the designed dimensions.

Further, in the case of electron beam exposure, it is easily affected by backscattering of electrons from the underlayer side and also easily affected by the proximity effect.

The disadvantage is that the pattern deteriorates and a beautiful, sharp resist pattern cannot be obtained.

Conventionally, a method of forming a three-layer resist pattern has been proposed for the purpose of preventing changes in pattern dimensions due to the influence of reflections due to unevenness of the substrate and deterioration of the pattern due to electron beam exposure (for example, in the document "Journal Of Vacuum Scientif 4-/ri Technology (J,
Vac, Sci.

Technol, , IL(8), Nov, /de
c, 11)79).

A method of forming such a conventional three-layer resist pattern will be briefly explained with reference to FIG.

FIG. 4 is a flowchart for explaining a method for forming such a resist pattern.

First, a single layer of polymer is spin-coated on the substrate as a base layer to flatten the irregularities of the substrate and to a thickness that can be used for etching the substrate (Step 3).
0) 0 The thickness of this lower layer is usually 1 to 2 tL.

Next, this single layer of polymer is baked at a high temperature to make it insoluble in a solvent (step 31).

Subsequently, 5i02 is deposited as an intermediate layer on this polymer layer (step 32), as this intermediate layer is a layer for transferring the resist pattern of the upper layer to the lower layer, which will be described later.
This Si02 layer is used because m-oxygen plasma property is required. .

Next, spin coat the top layer (step 33)
This upper layer is usually a resist layer sensitive to light, electron beams, X-rays, etc.

Subsequently, pre-baking was performed (after step 30, '
The upper layer is patterned by R light and development (step 35).

Next, using this patterned upper layer as a mask, the intermediate 5i02 layer is etched by dry etching (step 3B), and then the lower layer is dry etched using the intermediate layer as a mask (step 37).

In this way, a resist pattern with a three-layer structure consisting of a lower layer, an intermediate layer, and an upper layer is formed.

Another method is to use a siloxane compound instead of using 5102 as the intermediate layer.

In this case, after step 31, a siloxane compound is spin-coated as an intermediate layer on the lower layer as shown by the dashed line (step 38), followed by baking (step 38) and then the first step 33. The subsequent steps are similar to those described above.

According to these conventional resist pattern forming methods, the lower polymer layer appears to flatten the unevenness of the substrate, which prevents changes in pattern dimensions due to the effects of diffuse reflection and interference of light due to the unevenness of the substrate. Therefore, it became possible to form a pattern with high resolution and a large spectral ratio of 7.

(Problems to be Solved by the Invention) However, as is clear from the steps of the conventional forming method described above, the conventional method requires baking multiple times and also requires vacuum deposition. In some cases, the process for forming the multilayer structure as a whole is very long and complicated.

An object of the present invention is to provide a resist pattern forming method that can form a high-resolution, high-aspect-ratio footresist pattern with a high throughput using simple steps.

(Means for Solving the Problems) In order to achieve the object of the present invention, according to the resist pattern forming method of the present invention, after a lower layer, an intermediate layer, and an upper layer are deposited on the base layer, the upper layer is Then, using the patterned upper layer as a mask, the intermediate layer and lower layer are knee-etched to form a three-layer resist pattern. This intermediate layer is coated with novolac silyl ether. FIG. 1 shows a resist according to the present invention. This is a flowchart for explaining the basic steps of a pattern forming method, and steps similar to those shown in FIG. 4 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

According to the above-described structure of the present invention, a silyl ether of novolak is used as the intermediate layer.

Following the spin-coding of the lower layer (step 30), the intermediate layer is spin-coded (step lO), and then this intermediate layer is irradiated with short wavelength ultraviolet rays (step 2, step 11).
Then, the upper layer spin code is performed (step 33).

Thus, according to the method of the invention, since the intermediate layer is deposited by spin coating, 5i02
There is no need for a vacuum deposition process as in the case of calendars.

Furthermore, the purpose of irradiating the intermediate layer with short-wavelength ultraviolet rays is to make the intermediate layer insolubilized in solvents.To make this insolubilizable, as mentioned above, most of the resist is spin-coated on the intermediate layer as an upper layer. I can do it.

This eliminates the need for a pre-baking step for insolubilization, which was conventionally required between the formation of the intermediate layer and the upper layer.

Moreover, this resist can be easily removed using sulfuric acid or a commonly used organic solvent.

Due to these effects described above, the method of the present invention can significantly simplify the forming process compared to the conventional method.

Furthermore, since the resist has a multilayer structure, the effects of unevenness on the substrate can be removed by forming a lower layer with a flat surface, and the synergistic effect of this with the advantage of deep ultraviolet exposure creates a fine and sharp resist pattern. can be formed.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The examples described below are just examples, and conditions may vary depending on, for example, the dimensional accuracy of the intended final pattern, so the numerical values, shapes, materials, and other points with respect to the conditions described are The present invention is not limited to this embodiment.

2(A) to 2(H) of the support 1 unit are process diagrams for explaining one embodiment of the resist pattern forming method of the present invention.

First, a semiconductor substrate is used as the base layer 20, and this substrate 2
It is assumed that the surface of the substrate 0 has a step due to unevenness. The lower layer 21 is spin-coated onto this substrate surface, the convex portion being indicated by 20a (FIG. 2(A)). As this lower layer 21, a layer made of naphthoquinonediazide sulfonic acid ester of novolak (hereinafter referred to as NNE) is formed. This NNE film 21 was prepared by dissolving NNE in methylcellosolve acetate at a ratio of 30% by weight, filtering it with a 0.2 lu filter, and then spin coating it.
A film was formed with a film thickness of IL■.

Planarization was performed by filling in the steps on the substrate surface. (Figure 2 (A)
).

Next, after applying this NNE film 21, the intermediate layer 22 is
(FIG. 2(B)), this intermediate layer 22 is made by dissolving 7% by weight of novolac silyl ether (hereinafter referred to as NSE), such as trimethylsilyl ether, in xylene, and 0.2% by weight. After filtration with a final filter, a film with a thickness of 0.21 L was deposited by spin coating. This film 22 is referred to as an NSE film.

Thereafter, the entire surface of the NSE film 22 was irradiated with short-wavelength ultraviolet rays using a low-pressure mercury lamp (see Figure 2).
C)) In this case, the amount of ultraviolet irradiation (dose) is 2
J/cm2.

Next, the upper layer 23 was deposited on the intermediate layer 22 (12
Figure (D)), this upper layer 23 was formed by dissolving NNE in monochlorobenzene at a ratio of 10% by weight, filtering it through a filter with a diameter of 0.2 JL, and then spin coating it to a film thickness of 0.4 #L. It was filmed.

After that, the obtained sample was baked at a temperature of 80°C for 30 minutes, and then exposed to light using a Xe-Hg lamp by the Huntakt method (Fig. 2 (E)). was set at 20 mJ/c2.

After exposure, development was performed for 10 seconds with a mixed solution of 2 parts of cyclohexane to 10 of monochlorobenzene in a volume ratio, followed immediately by rinsing with cyclohexane for 20 seconds to perform patterning (Figure 2 (F). )), the temperature of the developer and rinse solution in this case was 23°C. Further, the etching holes (or grooves) removed and formed by this patterning are indicated by 23a.

When the pattern of the upper layer 23 thus obtained was observed with a scanning electron microscope, it was confirmed that the lines and spaces of the 0.5 JL intestine were resolved.

Thereafter, the obtained sample was placed in a parallel plate type plasma etching apparatus, and the middle layer 22 was etched using the pattern of the upper layer 23 as a mask (Fig. J2 (G)).
In this case, CF4 was used as the etching gas, the gas pressure was 5 Pa, and the power density was 0°18 W/am2 1. ．． ) Etching was performed for 3 minutes under the following conditions, with an amount of 50 scf and I. As a result, it was found that etching of the intermediate layer 22 could be performed satisfactorily using the upper layer 23. The etched hole (or groove) obtained in this case is indicated by 22a.

Next, the lower layer 21 was etched in the same parallel plate type etching apparatus by changing the etching gas to oxygen (02) gas (Fig. 2 (H)). In this case, the etching conditions were as follows: 5Pa, power density 0.08mm/
c2, the gas flow rate was 50 SCCN, and the etching time was 20 minutes. In this case, the upper layer 23 is etched and is not etched due to the oxygen plasma etching resistance of the intermediate layer 22, so that the portion of the lower layer 21 located below this intermediate layer is not etched, and therefore, Etching holes 21a are formed in the portions of the lower layer 21 exposed to the etching holes 22a of the intermediate layer 22, and the patterning of the lower layer 21 is completed, so that a three-layer structure as shown in FIG. 2(H) is formed on the base layer 20. A resist pattern is formed.

When the resist pattern thus obtained was observed using a scanning electron microscope, it was found to have a weight of 0.51b and a height of 2.5cm.
It was confirmed that a pattern of 0 p and ta was formed neatly and sharply.

In this example, the lower layer 2 is placed on the substrate 20 as in the example construction.
1 and an intermediate layer 22 were formed, and the intermediate layer 22 was irradiated with short-wavelength ultraviolet rays at a dose of 4 J/cm 2 using a low-pressure mercury lamp. After that, the upper layer 23 and TeAZ-1
350 (product name manufactured by Shipley) layer at 0.3p
A film was formed by spin coating to a thickness of m.

The obtained sample was baked at a temperature of 80° C. for 30 minutes, and then exposed to light using an ultra-high pressure mercury lamp with a mask in close contact with the sample. In this case, the exposure amount was 100 mJ/cm2.
Next, when the AZ-1350 developer was diluted with water at a ratio of 1:1 and the AZ-1350 layer 23 was developed for 15 seconds, the upper layer 23 was patterned to form a pattern of o, sp and p layer widths. I was able to form it.

After that, the middle layer 22 and the lower layer 21 were etched under the same conditions as in the example work, resulting in a beautiful and sharp three-dimensional pattern with a width of 0.8 mm and a height of 2.0 mm. A layered resist pattern was formed.

1凰1J In this example, a lower layer 2 is placed on a substrate 20 similar to Example I.
1. A layer of AZ-1350J (trade name manufactured by Shipley) was used as 2. A resist pattern could be formed in the same formation process as in Example I except for the areas coated with the thickness of the OJL layer. In this case, the etching time for the lower layer using oxygen plasma was 22 minutes. It was confirmed that the cross section of the three-layer resist pattern obtained in this example was steep, and that lines and spaces of 0.5-■ could be well formed.

The above-mentioned NSE can be obtained by silylating novolak with a silylating agent such as hexamethylene disilazane. The silylation rate is desirably 25 mo1% or more based on OH groups, because if it is less than 25 mo1%, the oxygen plasma resistance deteriorates and a sufficient etching selectivity with respect to the underlying layer cannot be achieved.

Although trimethylsilyl ether of novolak was used as the intermediate layer in each of the above-mentioned examples, the intermediate layer is not limited thereto. You can get the same effect as ether.

FIG. 3 is a diagram showing the experimental results regarding the oxygen plasma resistance of the novolac silyl needle used in the present invention. In the same figure, the horizontal axis shows the etching time in minutes (sin
), and the vertical axis shows the etching amount in gm. For comparison, the oxygen plasma resistance of AZ-1350J is also shown. From this experimental result, A
Even under conditions where Z-1350J is etched by about 2.01 Lm, the silyl ether of novolac is hardly etched by oxygen plasma, indicating that it has extremely good oxygen plasma etching resistance.

Furthermore, in the above-mentioned embodiments, etching of the silyl ether of novolak is performed using CF4 plasma, but the etching is not limited to this, and CF, +O, gas, or SF6 gas may also be used. In this case, it can be carried out by a conventional method similar to etching of 5i02 or siloxane.

Furthermore, etching of the underlying polymer layer can also be carried out using oxygen plasma in a conventional manner.

As is clear from the above explanation, this invention is characterized by the use of novolac silyl ether as the intermediate layer and the irradiation of this with short wavelength ultraviolet rays, so other points other than those mentioned above are It can be modified or changed as appropriate.

(Effect of the invention) As can be seen from the embodiments described above, according to the present invention,
Novolac silyl ether was used as the middle layer of the three-layer resist, so to form the three-layer film,
- Only one baking time is required.

Furthermore, since a vacuum evaporation process is not required, there is an advantage that the resist pattern forming process can be significantly simplified compared to the conventional method.

Furthermore, this novolak silyl ether has excellent oxygen plasma etching resistance, and is therefore extremely suitable for use as an etching mask.

Furthermore, novolak's silyl ether chill selb acetate, acetic acid ester, acetone, methyl isobutyl ketone, and other polar solvents, as well as benzene, chlorobenzene, toluene, xylene, and other nonpolar solvents, can be easily dissolved in novolac or novolak. In the case of a positive photoresist consisting of a photosensitive agent and a novolac-esterified NNF, it can be dissolved in chlorobenzene or xylene and coated.
Novolac silyl ether can be coated as an intermediate layer without damaging the underlying layer. Therefore, according to the method of the present invention, there is no need for the conventional step of baking the lower layer at a high temperature to make the lower layer insoluble in a solvent. It has the advantage that it can be formed by spin coating.

Furthermore, since the silyl ether of novolac is highly soluble in methylcellosolve acetate and chlorobenzene, which are normally used as solvents, it is not possible to immediately coat the upper layer on the intermediate layer consisting of the silyl ether of novolac. As in this invention, when this intermediate layer is irradiated with short-wavelength ultraviolet rays at a dose of 1 J/cm2 or more, the surface of the intermediate layer becomes insolubilized, so most of the resist remains on the irradiated intermediate layer. It has the advantage of being able to be coated with

[Brief explanation of drawings]

FIG. 1 is a process diagram for explaining the basic steps of the resist pattern forming method according to the present invention. FIGS. 2(A) to (H) are process diagrams for specifically explaining one embodiment of the resist pattern forming method of the present invention, and FIG. 3 is an oxygen-resistant plasma of novolac silyl ether used in the present invention. Diagram for explaining gender. FIG. 4 is a basic process diagram for explaining the conventional resist pattern forming method. 20... Base layer, 20a... Convex portion 21... Lower layer 21a, 22a, 23a... Etching hole 22...
Middle class, 23... Upper class. Patent applicant Oki Electric Industry Co., Ltd. Same as above Fuji Pharmaceutical Co., Ltd. Figure 1 Figure 4

Claims (1)

[Claims] (1) After depositing the lower layer, middle layer and upper layer on the base layer,
Forming a three-layer resist pattern by patterning the upper layer and then etching the intermediate layer and lower layer using the patterned upper layer as a mask, forming the intermediate layer from novolac silyl ether; A method for forming a resist pattern, which comprises irradiating the intermediate layer with short-wavelength ultraviolet rays all at once after forming the intermediate layer and before depositing the upper layer.