JP3130672B2 - Photomask pattern forming method - Google Patents

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 used for manufacturing a high-density integrated circuit such as an LSI and a super LSI, and more particularly to a method for forming a highly accurate resist pattern.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs and VLSIs are coated with a resist on a substrate such as a silicon wafer and exposed to a desired pattern by a stepper or the like.
It is manufactured by repeating a so-called lithography process such as development and etching.

A resist used in such a lithography process tends to be required to have higher precision with higher performance and higher integration of a semiconductor integrated circuit. For example, a DRAM which is a typical LSI is used. As an example, 1.2 μm for a 1 Mbit DRAM and 0.2 μm for a 4 Mbit DRAM.
There is a demand for further miniaturization of 0.6 μm for 8 μm and 16 Mbit DRAMs and 0.35 μm for 64 Mbit DRAMs, and various resists are being actively studied.

In general, the following characteristics are required for a resist material used for ultrafine lithography using a high-energy radiation source. (B) High sensitivity. (B) High resolution. (C) A uniform thin film can be formed. (D) Excellent dry etching resistance because dry etching essential for high-density fine patterning is applied. (E) Excellent developability.

Hitherto, a large number of resists used for the above-mentioned purposes have been developed. These resists include a positive type in which a chemical reaction is caused by irradiation with ionizing radiation to solubilize an irradiated portion, and a resist in which ionizing radiation is irradiated. Therefore, it is classified as a negative type in which a cross-linking reaction occurs and the irradiated part is insolubilized. Of these, the positive type has the disadvantage that the suitable range of the developer is generally narrow and the dry etching resistance is weak. On the other hand, many negative resists are superior to positive resists in these respects.

As an example of an electron beam resist which has been conventionally developed, a negative resist is CMS or PGM.
A and so on. This resist has a polymerizable functional group such as an epoxy group in the side chain and undergoes a cross-linking reaction by electron beam irradiation,
This means that the molecular weight increases and becomes insoluble in the developer. Further, positive resists include PBS, EBR-9, and the like. These resists are such that the main chain of the polymer is cut by irradiation with an electron beam, the molecular weight is reduced, and the resist is solubilized in a developer.

Recently, a chemically amplified resist excellent in sensitivity, resolution and dry etching resistance has been developed.
In this resist, an acid such as halogen acid is generated from an acid generator by irradiation with ionizing radiation, which acts as a catalyst for a crosslinking reaction (negative type) or a decomposition reaction (positive type), so that high sensitivity and high resolution can be obtained. It is known to be obtained.

FIG. 2 shows a step of forming a pattern of a chemically amplified negative resist. First, acid generator, crosslinking agent,
A chemically amplified negative resist 21 composed of three components of novolak resin is applied on a substrate 22 (A). Next, after exposure with ionizing radiation 23 such as an electron beam (B), heat treatment (C) with a hot plate or an oven or the like, development is performed to form a pattern 24 (D).

[0009]

As a resist for pattern processing in photolithography in the production of integrated circuits, only a positive resist is sufficient, but in electron beam lithography used in the production of photomasks, etc. It is more advantageous to use a positive resist or a negative resist depending on the type of pattern to be formed. In other words, when a resist pattern is formed by electron beam lithography on a photomask in which a thin film of chromium or the like is formed on a glass substrate, a pattern in which the thin film of chromium or the like remains largely and the portion that is removed little is a positive resist The exposure time is shorter when is used. Conversely, for a pattern having a small number of remaining portions and a large number of portions to be removed, the exposure time is shorter when a negative resist is used. Usually, two types of such resists are required, and each uses a dedicated resist and a resist processing step. Here, if there is a resist capable of obtaining both positive and negative patterns, only one type of resist is required, and the processing steps can be shortened.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of conventional resists, and has as its object to provide a method for forming a resist pattern for both positive and negative resists. The present inventors have studied to obtain a positive and negative resist, and as a result, neutralize the acid generated by treating the chemically amplified resist with an alkali after exposure, and then expose the entire substrate with ionizing radiation. As a result, it has been found that a positive / negative resist capable of reversing the image can be produced, and the present invention has been completed based on such findings.

That is, in the case of using a negative type chemically amplified resist, an acid is generated from an acid generator at an exposed portion by drawing with ionizing radiation after coating the resist. Next, baking is performed after exposure, and a pattern can be formed by a thermal crosslinking reaction. This is the usual method of forming a negative pattern, but the method of forming a resist pattern of the present invention draws a resist with ionizing radiation, generates an acid, and then exposes the resist to an alkaline atmosphere such as ammonia to neutralize the generated acid. Let it.
Next, rinse with water, etc., wash away the excess alkali, and then expose the entire surface of the resist with ionizing radiation.Acid is generated in places other than those drawn first with ionizing radiation, and then baking after exposure will remove the acid. By crosslinking, the image can be inverted.

The same applies to the positive type, where the acid generated from the acid generator is neutralized with an alkali, then rinsed with water or the like, the excess alkali is washed away, and then the entire resist is exposed to ionizing radiation. An acid is generated in a portion other than the portion drawn with ionizing radiation, and the acid generated by baking after exposure changes into a form in which the resist is dissolved in a developing solution, so that an image inverted by development is obtained.

The positive / negative resist of the present invention will be described below with reference to the drawings. FIG. 1 shows a pattern forming method using a chemically amplified negative resist. First, a chemically amplified negative resist 1 comprising three components of an acid generator, a crosslinking agent, and a novolak resin is applied on a glass substrate 3 on which a chromium thin film 2 is formed (A). Next, it is exposed to ionizing radiation 4 such as an electron beam to generate an acid 5 (B). Next, the resist is treated by dipping in an alkaline solution 6 such as an alkaline atmosphere 6 such as ammonia, an amine such as ethanolamine, or an alkaline salt such as sodium bicarbonate, or applied by spin coating to neutralize the generated acid (C ). PH of alkaline liquid used for neutralization treatment
Is preferably 8 or more.

Thereafter, when the entire surface of the substrate is exposed to ionizing radiation 7 (D) after removing the alkali from the resist with water or the like, acid 5 is generated in portions other than the drawing portion. The conditions for the reverse exposure may be any wavelength as long as the photosensitive group of the acid generator is exposed.When using a general chemically amplified resist for an excimer laser, use an electron beam, an excimer laser, or far ultraviolet rays. Can be. Exposure amount is 8 to 300 mJ / cm ²
It is preferable that

Next, a heat treatment 8 is performed on a hot plate or the like (E). Heating is preferably performed at 60 to 180 ° C. for 2 to 30 minutes. Next, development 5 is performed for 30 seconds to 10 minutes with an alkali such as tetramethylammonium hydroxide or sodium phosphate to form a resist pattern 9 whose image is inverted (F).

[0016]

According to the present invention, a chemically amplified resist capable of forming a fine pattern is alkali-treated after drawing,
The image to be formed can be inverted, and when forming a pattern using either a negative type or a positive type resist, it is possible to form both a negative type pattern and a positive type pattern it can.

[0017]

Embodiments of the present invention will be described below. Example 1 A chemically amplified negative resist SNR248 manufactured by Shipley Co. was applied on a chromium substrate to obtain a uniform resist film having a thickness of 600 nm. Next, after drawing with an electron beam of an acceleration voltage of 20 kV at an exposure amount of 2.5 μC / cm ² , the resist was placed on the upper surface of a container containing 1N ammonia water with the liquid surface side.
The substrate was exposed to an ammonia atmosphere for 10 minutes, and then rinsed with pure water. Next, the entire surface was exposed to light with a low-pressure mercury lamp for 10 minutes, placed on a hot plate, and heated at 120 ° C. for 5 minutes.
Finally, development was performed with a 2.38% aqueous solution of tetramethylammonium hydroxide for 2 minutes, followed by rinsing with pure water for 40 seconds, whereby a positive pattern with an inverted image could be formed.

[0018]

According to the present invention, it is possible to form both positive and negative patterns from either a positive or negative resist.
Both positive and negative resist patterns can be obtained using any one of the resists, so that the processing steps of the resist pattern are simplified.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for forming a resist according to the present invention.

FIG. 2 is a diagram illustrating a method of forming a resist pattern using a chemically amplified negative resist.

[Explanation of symbols]

1. Chemically negative resist, 2. Chromium thin film, 3.
Glass substrate, 4 ... ionizing radiation, 5 ... acid, 6 ... alkaline atmosphere, 7 ... ionizing radiation, 8 ... heat treatment, 9 ... resist pattern, 21 ... chemically amplified negative resist, 22 ... substrate, 23 ... ionizing radiation, 24 ... pattern

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 21/027 H01L 21/30 568 (58) Investigated field (Int.Cl. ⁷ , DB name) G03F 7/38 G03F 7 / 004 G03F 7/038 G03F 7/039 H01L 21/027

Claims (1)

(57) [Claims] In a method for forming a photomask pattern, after exposing a positive or negative type chemically amplified resist to a pattern by ionizing radiation, an acid in the resist generated by the exposure is neutralized with an alkali. A method for forming a photomask pattern, comprising: exposing the entire surface to ionizing radiation, developing the pattern, and forming a pattern using only one of a positive type and a negative type resist.