JPH0627668A - Negative resist sensitive to ionized radiation - Google Patents

Abstract

PURPOSE:To provide a high sensitivity and high resolution resist. CONSTITUTION:This negative resist contains a monomer generating an anion or cation by exposure with ionizing radiation 3 and a cationic or anionic polymer 2, a polymer having an anion or cation generating moiety and a cationic or anionic monomer, or a polymer having an anion or cation generating moiety and a monomer having a cation or anion generating moiety. When this resist is exposed with ionizing radiation 3, a polyion complex 4 is formed by the constituent monomer and polymer and a pattern is formed in this resist by the difference in solution velocity between the exposed and unexposed parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of high density integrated circuits such as LSI and VLSI, and more particularly to a high sensitivity and high resolution resist for forming a fine pattern with high accuracy.

[0002]

2. Description of the Related Art In semiconductor integrated circuits such as IC, LSI, and VLSI, a resist is applied on a substrate such as a silicon wafer and a desired pattern is exposed by a stepper or the like,
It is manufactured by repeating a so-called lithographic process such as development and etching.

The resist used in such a lithographic process tends to be required to have higher precision as semiconductor integrated circuits have higher performance and higher integration. For example, a typical LSI such as DRAM As an example, the drawn line width is 1.2 μm for a 1 Mbit DRAM, 0.8 μm for a 4 Mbit DRAM, 0.6 μm for a 16 Mbit DRAM, and 0.35 μm for a 64 Mbit DRAM.

In the conventional photolithography process, the circuit pattern is exposed by using ultraviolet rays. However, when the line width of the circuit becomes finer, the wavelength of the ultraviolet rays becomes a problem and accurate exposure becomes difficult. Instead, high-energy ionizing radiation such as electron beams has come to be used.

Generally, the following characteristics are required for a resist material used for ultrafine lithography using high-energy ionizing radiation and the like.

(A) High sensitivity.

(B) High resolution.

(C) It is possible to form a uniform thin film.

(D) Since dry etching, which is essential for high-density fine patterning, is applied, it is excellent in dry etching resistance.

(E) Excellent developability.

Conventionally, a large number of resists have been developed as the resists used for the above-mentioned purposes. These are a positive type in which the main chain of a polymer is cleaved by irradiation of ionizing radiation and the irradiated part is solubilized. It is classified as a negative type in which the irradiation part is insolubilized by a crosslinking reaction caused by irradiation with ionizing radiation.

Of these, the positive type generally has the drawbacks that the suitable range of the developing solution is narrow and the dry etching resistance is weak. On the other hand, the negative resist is
In many of these points, it is superior to the positive type.

Conventionally developed negative resists include CMS (chloromethylated polystyrene) and PGMA (polyglycidyl methacrylate). This resist had a polymerizable functional group such as an epoxy group in its side chain, and caused a crosslinking reaction upon irradiation with ionizing radiation.

Further, recently, a chemically amplified negative resist comprising three components of an acid generator, a crosslinking agent and a novolac resin has been developed. It is known that this resist produces high-sensitivity and high-resolution because an acid such as a halogen acid is generated from an acid generator upon irradiation with ionizing radiation, and this acts as an acid catalyst for a crosslinking reaction.

[0015]

As described above, the negative resists to date have a polymerizable bond site such as a double bond or an epoxy group in the side chain of the polymer, and that part is exposed to the ionizing radiation. It was excited, radicals were generated, and the polymerization reaction proceeded. However, in such a negative resist, active radicals generated are chain-transferred, so that scum is easily generated and the resolution thereof is extremely poor. Further, since it is difficult to introduce an aromatic ring into the molecular structure, the dry etching resistance was not satisfactory.

A chemically amplified negative resist composed of three components of an acid generator, a cross-linking agent and a novolak resin produces an acid such as a halogen acid from the acid generator upon irradiation with ionizing radiation, and the acid is cross-linked. Since it acts as a catalyst for the reaction, it is known for its high sensitivity and high resolution. However, the stability of the acid generator is extremely poor, and there is a problem in that a step of heating after exposure is required to cause a crosslinking reaction.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of conventional resists, and an object of the present invention is to provide a negative resist having high sensitivity and high resolution.

The inventors of the present invention have conducted research to obtain a resist that enables ultrafine lithography, and as a result, have formed a polyion complex between a monomer that produces an anion or a cation by ionizing radiation and a cationic or anionic polymer, or an anion or a cation. The exposed portion is formed by forming a polyion complex between a polymer having a site that produces a cation and a cationic or anionic monomer, or forming a polyion complex between a polymer having a site that produces an anion or a cation and a monomer having a site that produces a cation or an anion. It was found that a negative resist can be produced due to a difference in dissolution rate between the unexposed portion and the unexposed portion, and the present invention has been completed based on such findings.

In a negative type resist such as CMS, radicals generated by irradiation of ionizing radiation are chain-transferred and swelled by a developing solution at the time of development, so that the resolution was not very good. In the present invention, only the portion irradiated with ionizing radiation is ionized and a complex is formed only in that portion, so that the chain transfer reaction does not proceed. Further, unlike the case where a crosslinking agent is used, the molecular weight does not increase due to the crosslinking reaction, so that it does not swell during development. Therefore, it becomes possible to obtain a resist of ultra-high resolution.

Further, in the case of a three-component chemically amplified negative resist, it is necessary to heat it after exposure to cause a crosslinking reaction. In the present invention, since the anion or cation generated by the irradiation of ionizing radiation forms a polyion complex with ions of opposite charges existing in the vicinity, after the exposure for the crosslinking reaction which is performed in the chemically amplified negative resist. The heating step can be omitted.

Further, the stability of the resist can be improved by using an orthodiazonaphthoquinone derivative known as a photosensitizer of an azide type resist as an anion generator.
Its stability improves.

The negative resist of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a reaction scheme of the negative resist of the present invention, where 1 is a monomer having a site for generating a cation and 2 is an anionic polymer.

Examples of anion generators include orthodiazonaphthoquinone and its derivatives, and cation generators include triphenylmethanol and its derivatives.

First, as shown in FIG. 1 (a), an equimolar (per monomer unit) amount of a mixed solution of a monomer having a site for generating an anion and a cationic polymer is prepared and spin-coated on a substrate. Is uniformly applied by a conventional method, heat-dried, and the thickness is 0.1 to 2.0.
A resist film of about μm is provided. The heat drying treatment is usually 20 to 6 at 80 to 150 ° C., though it depends on the type of resist.
Do it for 0 minutes.

Next, by irradiation with ionizing radiation 3, the generated cations and anionic polymers form a polyion complex 4 as shown in FIG. 2B, and the polarity changes. When the finally exposed substrate is treated with an alkali developing solution or the like, a difference in solubility in the developing solution occurs between the irradiated portion and the non-irradiated portion, so that various patterns can be formed.

The mechanism by which a triphenylmethanol derivative produces cations when irradiated with ionizing radiation will be shown below. When the triphenylmethanol derivative is irradiated with the energy of ionizing radiation, the hydroxyl groups are dissociated to generate cations.

[0027]

[Chemical 1]

The mechanism by which an orthodiazonaphthoquinone derivative produces an anion when irradiated with ionizing radiation is shown below. When an orthodiazonaphthoquinone derivative is exposed to ionizing radiation, it produces a ketene, which in the presence of water molecules subsequently yields two acids, a carboxylic acid and a sulfonic acid, as shown here. Since carboxylic acid is a weak acid, it is neutral or alkaline,
Present as a carboxylate. Since sulfonic acid is a strong acid, it exists as a sulfonate except in a fairly strong acidic region. As a result, it is possible to form an ion complex with a cationic polymer that is a counter ion.

[0029]

[Chemical 2]

[0030]

[Function] With the recent higher integration of LSIs and VLSIs, resists with higher sensitivity and higher resolution are required, and those having good dry etching resistance and stability are desired. In the invention, since the negative pattern can be formed using the polyion complex without a crosslinking reaction,
A cross-linking reaction step by heating after exposure is not necessary, and highly precise pattern drawing is possible in terms of resolution without swelling during development.

[0031]

EXAMPLES Examples of the present invention will be described below. Example 1 Triphenylmethanol shown below and potassium polyvinylsulfonate as an anionic polymer were mixed with 2-ethoxyethyl acetate in an equimolar amount (per monomer unit) to obtain a resist solution.

[0032]

[Chemical 3]

This resist solution was applied on a chrome mask substrate by a scopin coating method, and the temperature was increased to 30 ° C. at 120 ° C.
Prebaking was performed for a minute to obtain a uniform resist film having a thickness of 500 nm. Next, a beam diameter of 0.05 μm is applied to this resist film,
It was irradiated with an electron beam having an energy of 10 keV. After irradiating with changing the exposure dose, this is applied to an alkaline aqueous solution.
The irradiated portion was insolubilized by immersing for 2 seconds for development and further rinsing with pure water. A pattern with a sensitivity of 3 μC / cm ² and a resolution of 0.1 μm was formed.

[0034]

INDUSTRIAL APPLICABILITY The resist using the polyion complex of the present invention can form a negative pattern without forming a cross-linking reaction by forming an ion complex of anions and cations. It features high sensitivity and high resolution without fear. Further, by incorporating a novolac resin or silicone in the polymer, it is possible to manufacture a resist having dry etching resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing a reaction scheme of a negative resist using a polyion complex.

[Explanation of symbols]

1 ... Cation generator, 2 ... Anionic polymer, 3 ... Ionizing radiation, 4 ... Polyion complex

Claims (1)

[Claims] 1. A negative resist sensitive to ionizing radiation, characterized in that a monomer or polymer having a site for generating an anion or a cation by ionizing radiation, a polymer having a counter ion thereof, and the monomer form a polyion complex.