JPH11135397A - Forming method for negative type resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which an advantage of a surface imaging method using a resin material which has an aromatic ring structure, having high dry etching resistance and a negative type pattern is formed with high sensitivity, even in the case of a light lithography using an ArF excimer laser light source. SOLUTION: A lower layer resist 2 having a surface layer part comprising components including an aromatic ring and having a functional group which is protected by an acid decomposing group is formed on a substrate 1, a photosensitive layer 3 which is made of an applying material, virtually not having an absorbing band in an ArF excimer laser exposure wavelength and an acid precursor is formed thereon, a predetermined pattern exposure is performed, and acid is made to be generated at the exposure part. The functional group which is protected by the acid resolving group of the lower layer resist 2 contacting with the acid generating part 5 is protected. The photosensitive layer 3 is eliminated, the surface which is protected is exposed and processed by an reactive organic metal regent, and the lower layer resist 2 is exposed in an oxidizing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern required for manufacturing a semiconductor device or an integrated circuit.
More specifically, a high-pressure mercury lamp, which is a current ultraviolet light source, and an ArF, which is a shorter wavelength source than a KrF excimer laser, are used.
The present invention relates to a method for forming a negative resist pattern that can be used in deep ultraviolet lithography using an excimer laser as a light source.

[0002]

2. Description of the Related Art A photolithography technique for forming a fine pattern on the order of microns or submicrons in an electronic device such as a semiconductor has played a central role in mass production fine processing technology. The recent demand for higher integration and higher density of semiconductor devices is
Many advances have been made in microfabrication technology. In particular, as the minimum processing size approaches the exposure wavelength, photolithography technology using a KrF excimer laser (248 nm) from a g-line (436 nm) and i-line (365 nm) of a high-pressure mercury lamp and a shorter wavelength light source is developed. It has been. In response to these changes in the exposure wavelength, materials corresponding to the respective wavelengths of the photoresist have been developed.

Conventionally, photoresists suitable for these wavelengths have different photosensitizers or photosensitive mechanisms. However, aqueous alkali development utilizing the aqueous alkali solubility of a resin or a polymer material having a phenolic hydroxyl group is industrially required. Has been used for These resins or polymer materials inevitably contain a large amount of aromatic rings, which was also a chemical structural element for improving the etching resistance in a dry etching step after the formation of a resist pattern.

[0004] Far ultraviolet lithography using an ArF excimer laser as a light source uses light having a shorter wavelength than a high-pressure mercury lamp or a KrF excimer laser, which is an ultraviolet light source used in current optical lithography, so that higher optical resolution performance can be expected. However, the wavelength of the ArF excimer laser light (193)
nm), most of high-performance resists using a resin or a polymer material having a phenolic hydroxyl group, which have been widely used, cannot be used. This is because the molecular structure of the aromatic ring contained in the main components of these resist materials has an extremely large absorption band near the wavelength of ArF excimer laser light. That is, even if these resists are subjected to pattern exposure with ArF excimer laser light, exposure is limited to the vicinity of the very surface of the resist, and a latent image in the thickness direction of the resist cannot be practically formed.

The advantages of surface imaging techniques that limit the exposure latent image to near the surface of the resist are generally well known. A mask resistant to oxygen plasma etching by being selectively treated with an organometallic compound, for example, a silylating agent such as hexamethyldisilazane, trimethylsilyldimethylamine, or bisdimethylaminomethylsilane, based on an exposure latent image on the resist surface. There is a method in which a pattern is formed on the resist surface, and the surface mask pattern is transferred to the resist film by reactive ion etching of oxygen or the like. This reactive ion etching has a high anisotropy, so the resist image after transferring the surface pattern generally has a large aspect ratio, and since the exposure latent image is on the resist surface, there is a problem with the substrate step which is a problem with a single-layer resist. It is known that it is hardly affected by reflection and halation due to light.

US Pat. No. 5,023,164 uses a resist material consisting of a novolak resin in which a hydroxyl group is protected with an acid-decomposable group and an acid generator, and forms a pattern by using deep ultraviolet rays or vacuum ultraviolet rays having a large absorption on the resist surface. Exposure, a method of deprotecting the acid-decomposable group with an acid generated in an exposed portion, and further reacting the organometallic compound with the resist film to form a pattern having reactive ion etching resistance on a pattern-exposed surface. It has been disclosed.

However, the absorbance of a resin containing an aromatic ring, such as a novolak resin, at the wavelength of ArF excimer laser light reaches about 20 per 1 μm of film thickness, which is 0.1 μm from the resist surface. That means that the rate is already around 1%. Therefore, as long as an aromatic resin such as a novolak resin is used for the matrix of the resist, it becomes extremely difficult for a photosensitive component in the resist such as a photoacid generator to undergo a photochemical reaction by direct exposure. That is, in the above-mentioned known example, a considerable amount of exposure is required to induce a deprotection reaction on the resist surface using ArF excimer laser light, and there is a problem that the effective sensitivity is extremely reduced.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an advantage of a surface imaging method using a resin material having an aromatic ring structure having high dry etching resistance, and an ArF
An object of the present invention is to provide a method for forming a negative pattern with high sensitivity even in optical lithography using an excimer laser light source.

[0009]

The object of the present invention is to provide an optical lithography method for forming a negative resist pattern in a predetermined pattern on a predetermined substrate by using an ArF excimer laser as a light source. Forming an underlayer resist having a surface layer portion comprising an aromatic ring and having a sensitive group protected by an acid-decomposable group, and (2) forming an absorption band on the underlayer resist substantially at the exposure wavelength. Forming a photosensitive layer comprising a coating material having no coating material and an acid precursor, (3)
The photosensitive layer is exposed in a predetermined pattern to generate an acid in an exposed portion corresponding to the predetermined pattern. (4) A photosensitive layer protected by an acid-decomposable group of a lower resist in contact with the acid generating portion corresponding to the exposure. Deprotecting the group, (5) removing the photosensitive layer,
(6) treating the exposed lower-layer resist with a reactive organometallic reagent, and (7) subjecting the exposed lower-layer resist to an oxidizing atmosphere. This is achieved by a method for forming a negative resist pattern, comprising a step of generating a negative resist pattern by exposing the resist.

The photosensitive layer used in the present invention is made of a coating material having substantially no absorption band at the wavelength of exposure from an ArF excimer laser, for example, a water-soluble polymer such as polyvinyl alcohol or polyacrylic acid and an acid compatible therewith. Precursors, for example, additives comprising water-soluble onium salts such as phenyldimethylsulfonium trifluoromethanesulfonate and trimethylsulfonium p-toluenesulfonate, which additionally suppress the diffusion of acids generated by exposure in the direction of the coating film surface. May be included.

According to the present invention, since the coating material, which is a main component, has substantially no absorption band at the exposure wavelength, the exposure energy can be effectively used, and the latent image having a predetermined pattern shape composed of an acid generator is provided. Can be formed with high sensitivity.

In addition, since the lower resist layer contains many aromatic rings exhibiting extremely large absorption at the exposure wavelength from the ArF excimer laser, it has the advantage of the surface imaging method that it is not affected by reflection from the substrate surface or halation, and This material has resistance to dry etching used for substrate processing. Since an acid-decomposable group in the lower resist at the interface between the photosensitive layer and the lower resist layer is decomposed by an acid-catalyzed reaction using an acid generated in the photosensitive layer, a surface latent image can be formed on the lower resist surface with high sensitivity.

After the photosensitive layer is removed, an organic metal compound such as a silylating agent such as hexamethyldisilazane, trimethylsilyldimethylamine or bisdimethylaminomethylsilane is selectively reacted with the surface latent image. ,
The surface latent image portion is modified to a compound containing a metal such as silicon having a property capable of reacting with oxygen plasma or the like to be transformed into a nonvolatile metal oxide. On the surface corresponding to the unexposed portion, the above-described acid-catalyzed reaction does not proceed, the sensitive group in the lower resist remains protected, and the surface is not subjected to such modification.

A step of exposing the lower layer resist having a surface latent image of a predetermined pattern modified with an organometallic compound to an oxidizing atmosphere, for example, oxygen plasma or reactive ion etching of oxygen, or an atmosphere containing oxygen or ozone; In the step of photo-oxidation etching below, the unexposed portion remains as the organic resin and is oxidized and removed.However, the surface latent image forming portion of the exposed portion is transformed into a nonvolatile oxide and further etched. A negative-type pattern can be formed without the need.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments, but the present invention is not limited to these.

The case where poly (p-tetrahydropyranyloxystyrene) is used as the composition of the lower resist surface layer will be described with reference to the process chart of FIG.

A cresol novolak resin (polystyrene equivalent weight average molecular weight of about 19,00
0) from a methyl amyl ketone solution by a spin coating method,
It is heated at 120 ° C. for 2 minutes to form a resin film having a thickness of about 0.8 μm. Furthermore, poly (p-tetrahydropyranyloxystyrene) was applied thereon from a xylene solution,
2 ° C. for 2 minutes to form 0.2 on the novolak resin film.
The lower resist 2 is made to have a thickness of 5 μm and a total of about 1.05 μm. 1 part by weight of a 5% by weight aqueous solution of polyvinyl alcohol (trade name: Kuraray Poval # 224), 2 parts by weight of a 5% by weight aqueous solution of a polyacrylic acid aqueous solution (manufactured by Wako Pure Chemical Industries), and a photosensitizer (photoacid generator) An aqueous solution containing 0.05 parts by weight of phenyldimethylsulfonium trifluoromethanesulfonate as an agent) is dropped on the lower resist, spin-coated and heated at 100 ° C. for 2 minutes to form a photosensitive layer 3 having a thickness of about 0.2 μm. Form. Next, an acid generator 5 corresponding to the predetermined pattern shape is formed in the photosensitive layer 3 by exposure 4 having a predetermined pattern shape using an ArF excimer laser light source (FIG. 1A). At this time, the exposure amount was 15 mJ / cm 2.

The substrate on which the acid generating portion 5 is formed in the photosensitive layer 3 is heated at 100 ° C. for 3 minutes so that the poly (p-tetrahydropyranyloxystyrene) in the portion of the lower resist 2 in contact with the acid generating portion 5 is heated. 2), the acid in the acid generator 5 is diffused and allowed to act to form a latent image area 6 in which the tetrahydropyran group is deprotected (FIG. 1B).

The photosensitive layer 3 including the photosensitive portion (acid generating portion) is removed by washing with water (FIG. 1c). A latent image area 6 is formed in a poly (p-tetrahydropyranyloxystyrene) portion on the upper surface of the lower resist, and a hydroxyl group is formed in this portion as a reactive sensitive group.

After the substrate is sufficiently dried by heat treatment at 120 ° C. for 2 minutes, the surface of the substrate is treated in hexamethylene disilazane vapor at 60 ° C. for 15 minutes to obtain a latent image on the lower resist. A silylated image 7 is formed on the surface of the region 6 (FIG. 1d). Hexamethylene disilazane reacts with hydroxyl groups in the latent image area to silylate that part, but the other lower resist surface must be silylated because the hydroxyl groups are all protected by tetrahydropyranyl groups. There is no.

The sample having the silylated image 7 formed on the surface of the lower resist is subjected to photo-oxidation treatment in an oxygen atmosphere using an optical asher device equipped with a xenon dielectric barrier discharge excimer lamp (UER 20-172 manufactured by Ushio Inc.). As a result, the silylated image forming portion was oxidized to form a non-volatile silicon oxide image 8, and a negative pattern in which the silylated image was faithfully transferred was formed in the lower resist portion (FIG. 1).
e). Further, the lower resist which was not silylated was almost completely photooxidized, and no solid residue was observed at all, and was almost completely removed.

The wavelength of the light from the lamp is 172 nm. At this wavelength, the lower resist containing an aromatic ring structure shows an extremely large absorbance, and almost all of the exposure energy is absorbed up to near its very surface. Therefore, the exposed portion of the lower resist is sequentially photooxidized from the surface under an oxygen atmosphere, whereas the silylated surface portion is exposed to the surface when the non-volatile silicon oxide is formed by photooxidation. The lower portion is shielded from oxygen and ozone generated from oxygen by light from a lamp, and oxidation does not proceed any more. Further, since the light from the lamp does not pass below the lower resist electrode surface, side etching is also suppressed.

[0023]

According to the present invention, a negative pattern having a high aspect ratio is applied to a lower resist having an aromatic ring structure having high sensitivity even at the wavelength of ArF excimer laser light and having high dry etching resistance by a surface imaging method. The lithography technique using an ArF excimer laser light source enables fine processing of a highly integrated semiconductor device to be realized with high accuracy and high efficiency.

[Brief description of the drawings]

FIG. 1 is a process chart of a method for forming a negative resist pattern according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Lower layer resist, 3 ... Photosensitive layer, 4 ... ArF
Excimer laser exposure, 5: photosensitive part (acid generating part), 6: latent image area, 7: silylated image, 8: oxide image, 9: negative resist image.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/302 H (72) Inventor Yui Arai 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (3)

[Claims] 1. An optical lithography method for forming a negative resist pattern in a predetermined pattern on a predetermined substrate by using an ArF excimer laser as a light source, wherein (1) the predetermined substrate contains an aromatic ring and is acid-decomposed. Forming a lower layer resist having a surface layer composed of a composition having a sensitive group protected by a functional group, and (2) forming a coatable material having substantially no absorption band at the exposure wavelength on the lower layer resist and an acid precursor. A photosensitive layer composed of a body is formed, (3) the photosensitive layer is exposed in a predetermined pattern, an acid is generated in an exposed portion corresponding to the predetermined pattern, and (4) an acid generating portion corresponding to the exposure is generated. Deprotect the sensitive group protected by the acid-decomposable group of the lower resist,
(5) removing the photosensitive layer and exposing the surface of the lower resist in which the sensitive group protected by the acid-decomposable group has been deprotected,
(6) negatively treating the exposed lower-layer resist with a reactive organometallic reagent, and (7) exposing the lower-layer resist to an oxidizing atmosphere to form a negative resist pattern. Method of forming mold resist pattern. 2. The method for forming a negative resist pattern according to claim 1, wherein said photosensitive layer is substantially made of a water-soluble material, and is applied from an aqueous solution. 3. The method for forming a negative resist pattern according to claim 1, wherein the step of exposing the lower resist to the oxidizing atmosphere to generate a negative resist pattern includes oxygen gas or ozone. A method of forming a negative resist pattern, comprising a step of photo-oxidizing etching of the lower resist in an isotropic oxidizing atmosphere.