JPS6260691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microfabrication method that utilizes a radiation-sensitive resist, particularly a negative resist, in the manufacture of semiconductor integrated circuits.

The etching process in the manufacture of semiconductor integrated circuits includes
2. Description of the Related Art Conventionally, a method of forming an etched pattern using a photosensitive resin (photoresist) sensitive to visible light and ultraviolet light has been widely put into practical use. In recent years, in order to improve the reliability and performance of integrated circuits, there has been an increasing demand for higher density and higher integration of elements, and vigorous research is being carried out with the aim of establishing ultra-fine circuit pattern technology. Among these, methods have been developed for forming highly accurate circuit patterns using high-energy radiation such as deep ultraviolet rays, X-rays, and electron beams with short wavelengths instead of conventional light beams. Along with this, it is essential to develop high-performance resist materials that are sensitive to these radiations. When manufacturing integrated circuits, a fine pattern is formed by coating a resist material on a substrate to form a thin film, exposing it to radiation, and developing it. A method of etching the substrate other than the pattern forming area is adopted. In this integrated circuit manufacturing process, high sensitivity and high resolution are important performance requirements for resists, and in particular, with regard to resolution, resist materials that can handle submicron microfabrication precision of 1 μm or less are important. is required. Furthermore, in the etching process, wet etching using chemicals has traditionally been used, but it is not suitable due to side etching effects, and dry etching using gas plasma, reactive sputtering, etc. is used for submicron microfabrication. It is now moving into processing. Therefore, a material with excellent dry etching resistance is required as a resist material. Several radiation-sensitive resist materials for microfabrication have been developed to date, but very few of them satisfy all of the above required performances. For example, glycidyl methacrylate polymer (PGMA) is known as a negative resist material, but although its sensitivity to electron beams is as high as 10 ^-7 C/ ^cm2 , its resolution is insufficient, and it is difficult to dry-etch. The drawback is that it lacks durability. On the other hand, methyl methacrylate polymer (abbreviated as PMMA), which is known as a positive resist material, has a γ value of 2.5, which is a measure of resolution.
Although it has been confirmed that large, submicron fine patterns can be formed, the sensitivity to electron beams is 10 ^-4 to ^{10 -5} C/cm ² , which is below practical sensitivity. PGMA for dry etching resistance
Although it is better than that, it is still not sufficient.
A resist material containing an aromatic ring in the repeating unit structure of a polymeric material is known as having excellent dry etching resistance, but the resist material is a photoresist and has poor sensitivity to radiation.

The present inventors have arrived at the present invention as a result of intensive research aimed at improving the problems seen in these conventional resist materials. The present invention provides a microfabrication method comprising forming a thin film of a radiation-sensitive polymer on a substrate, irradiating it with radiation, and then developing and etching it, in which the polymer has the general formula: (However, in the formula, R and R' are hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 3 representing the number of substituents) at least 10% by weight or more. This is a microfabrication method using a radiation-sensitive resist material that is characterized by being a heavy body containing radiation, and its purpose is to produce a negative-tone radioactive resist material that is highly sensitive to radiation, has good resolution, and has excellent dry etching resistance. The purpose of the present invention is to provide a microfabrication method using a sensitive resist material.

By introducing an aromatic ring into the repeating unit structure of the polymeric substance used as the resist material used in the present invention, it imparts dry etching resistance and at the same time has high sensitivity to radiation, -CH ₂ NR. The present invention attempts to obtain a resist material having high sensitivity to radiation by incorporating an aminomethyl group or a dialkylaminomethyl group represented by ' ₂ as a substituent in an aromatic ring. Furthermore, the polymer substance is preferably a polymer with a narrow molecular weight distribution, and the weight average molecular weight (
More preferably, the dispersity defined by the ratio w/n of w) and number average molecular weight (n) is, for example, 1.1 or less.
At 1.05 or less, a nearly monodisperse polymer can be obtained. In other words, it is an attempt to provide a negative resist material for microfabrication that has good resolution and dimensional accuracy of 1 μm or less.

The polymer substance used in the present invention is a polymer containing at least 10% by weight or more preferably 20% by weight or more of repeating units represented by the above general formula, and the polymer includes (i) repeating units represented by the above general formula; They are broadly classified into homopolymers consisting only of units and (ii) copolymers consisting of two or more types of repeating units containing repeating units represented by the above general formula.
The copolymer component in (ii) above is not particularly limited, but includes, for example, heterocyclic compounds such as vinylpyridine, styrene, α-methylstyrene, chloromethylstyrene, bromomethylstyrene, halogenated styrene, etc. Examples include styrenic and halogen-containing styrene compounds, and methacrylic acid esters such as glycidyl methacrylate. There is no need to particularly limit the molecular weight of these polymeric substances, but considering that the sensitivity to radiation depends on the molecular weight, it is desirable to set the molecular weight to 5,000 or more, preferably 10,000 or more.

Examples of a resist material manufacturing method and a microfabrication method using the resist material will be described in detail below.

Example 1 A homopolymer of 4-vinylbenzyldimethylamine (abbreviated as 4VBDMA) was obtained by an anionic polymerization method. That is, 4VBDMA that had been strictly dehydrated and purified was polymerized in a benzene solvent using sec-butyllithium as an initiator in a conventional manner. The molecular weight of the obtained polymer was determined to be 1.7×10 ⁵ by light scattering measurement. In addition, as a result of evaluating the molecular weight distribution using the ultracentrifugal velocity method,
The degree of dispersion was 1.01 or less, confirming that the polymer was close to monodisperse.

The obtained 4VBDMA polymer was subjected to microfabrication as an electron beam resist material. 10% by weight of the polymer
Dissolved in ethylsolve acetate at a concentration of . A uniform thin film with a thickness of about 0.6 μm was formed on a silicon substrate by spin coating. After heat treating this in vacuum at 100°C for 30 minutes, a pattern was drawn using an electron beam exposure device (acceleration voltage: 20 KV). After electron beam irradiation, the film was developed for 3 minutes using a mixed solvent of methyl ethyl ketone and ethanol (1:1 volume ratio) and rinsed with ethanol. Electron beam irradiation amount (C/cm ² )
The residual film rate was measured and the results are shown in FIG. When the sensitivity is defined as the irradiation dose for a residual film ratio of 0.5, the sensitivity is 1.6×10 ^-6 C/cm ² from this figure, which is more than 50 times higher than that of polystyrene of the same molecular weight.

As a result of examining the resolution of this resist material by changing the line/space dimensions as a pattern drawn with an electron beam, the line width was 0.2 μm and the space was 0.4 μm.
m fine patterns were resolved. It is clear that this resist material can be used for submicron microfabrication. Moreover, the resolution index calculated from the curve in FIG. 1 is a large value of 10 or more, which is a result that supports the high resolution of this resist material.

Example 2 A 4VBDMA polymer having the same chemical structure as the polymer of Example 1 and having a small molecular weight was obtained by the same manufacturing method as in Example 1. The molecular weight was 5.4×10 ⁴ . The sensitivity and resolution of this polymer as an electron beam resist were evaluated in substantially the same manner as in Example 1. The sensitivity was 5×10 ⁻⁶ C/cm ² , and a pattern with a line width of 0.2 μm was formed.

The dry etching resistance of this polymer was investigated. A cylindrical plasma reactor (frequency: 3.56 MHz, output: 200 W) was used to measure the etching rate of carbon tetrafluoride reaction gas plasma containing 5% by volume of oxygen. For comparison, polystyrene,
The etching rate of PMMA was also measured under the same conditions. After 15 minutes, the etching depth of each polymer thin film was measured and found to be 800 Å for 4VBDMA polymer, 500 Å for polystyrene, and 4000 Å for PMMA.
Although the etching resistance of the 4VBDMA polymer is slightly inferior to that of polystyrene, it has been found that the etching resistance of the 4VBDMA polymer is 6 to 7 times better than that of PMMA. In addition,
No molecular weight dependence on dry etching resistance of 4VBDMA polymer was observed.

Example 3 Monodisperse polystyrene obtained by anionic polymerization method (
w=1.07×10 ⁵ , w/n=1.01) using chloromethyl methyl ether as the chloromethyl mower,
In addition, after partial chloromethylation using tin tetrachloride as a catalyst (degree of chloromethylation: 54%), complete reaction with dimethylamine resulted in the substitution of dimethylamino groups on the benzene ring of polystyrene (degree of substitution).
54%) copolymer was obtained.

The properties of this polymer as an electron beam resist were investigated in the same manner as in Example 1. The sensitivity to electron beams was 4×10 ⁻⁶ C/cm ² , and a fine pattern with a line width of 0.3 μm was formed. Further, as a result of measuring the etching rate of this polymer against plasma under the same conditions as in Example 2, it showed almost the same etching resistance as the 4VBDMA homopolymer.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the electron beam irradiation amount and the residual film rate for the 4VBDMA polymer obtained in Example 1. Figure 2 was obtained in Example 1.
This is an electron micrograph of a fine pattern formed using 4VBDMA polymer. Line width 0.2μm,
The space is 0.4 μm.

Claims (1)

[Claims] 1. A microfabrication method comprising forming a thin film of a radiation-sensitive polymer on a substrate, irradiating it with radiation, developing and etching it, wherein the polymer has the general formula: (However, in the formula, R and R' are hydrogen or an alkyl group, and n is an integer representing the number of substituents.) At least 10% by weight of repeating units represented by
A microfabrication method using a radiation-sensitive resist material characterized by being a polymer containing the above.