JPH042183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for forming an electron beam resist pattern.

(b) Background of technology Electronic circuit elements, as typified by semiconductor devices such as ICs and LSIs, are becoming smaller and more integrated, and various patterns including conductor patterns are becoming extremely fine. converted is used.

For example, the width of conductor patterns in ICs and LSIs has been reduced to about 1 μm.

Conventionally, thin film formation technology and photolithography have been used to form fine patterns.

Here, photo-etching technology takes advantage of the fact that a photoresist is coated on the substrate to be processed by a method such as spin coating, and then selectively exposed to ultraviolet rays through a mask, which causes a difference in solubility of the light irradiated area with respect to the developer. There are two types of image forming molds: a negative type in which the light irradiated area is insoluble in the developer, and a positive type in which the light irradiated area is soluble.

Now, in the conventional method of forming fine patterns by exposure to ultraviolet rays, it is limited to patterns with line widths of 1 μm or more due to wavelength limitations, and it is impossible to form patterns with fine line widths of less than 1 μm.

On the other hand, the wavelength of an electron beam varies depending on the accelerating voltage, but it is about 0.1 Å, which is much shorter than 0.1 μm.
It is also possible to form a wide pattern.

For this reason, electron beam exposure is used instead of conventional ultraviolet ray exposure to form fine patterns, and therefore the resist used has also changed from photoresist to electron beam resist.

The present invention relates to a method for forming a fine pattern on a substrate having irregularities using a positive electron beam resist.

(c) Prior Art and Problems As a method of achieving high integration of circuit elements, multilayer wiring patterns are used.

For example, in the case of semiconductors, a thin film of aluminum (Al) or poly-Si is formed on a silicon (Si) single crystal substrate, a conductive pattern is created by etching this, and then a phosphosilicate glass (abbreviated as
A layer of PSG) or silicon dioxide (SiO ₂ ) is often formed to insulate the layer and intersect with the underlying conductor layer to form a conductor pattern.

In such a case, since the lower conductor pattern existing portion is raised to create a step, defects such as wire breakage are likely to occur when forming a fine pattern across this raised portion.

The reason for this is that dry etching, especially reactive ion etching (abbreviated as RIE), which has directional etching, is used instead of conventional chemical etching from the viewpoint of precision in etching fine patterns. The thickness of the resist layer formed by methods such as the coating method becomes thinner at the edge of the step, so the resist in this area does not play the role of a mask and disappears before the etching of the substrate to be processed is completed, making it difficult to form a pattern. Wire breakage occurs easily, and dimensional accuracy is not achieved.

To solve this problem, a multilayer resist method is being used.

A to C in FIG. 1 illustrate this method, in which a planarizing layer 2 is formed by thickly coating an organic resin on a substrate 1 to be processed having irregularities, and a planarizing layer 2 with excellent dry etching resistance is applied on top of the planarizing layer 2. After selectively exposing and developing the upper resist layer 3 to form a window 4, dry etching is performed using the upper resist layer 3 as a mask to process the substrate 1. This is used to form patterns.

Since the flattening layer 2 is etched using oxygen plasma, the resist layer 3 is made of a material resistant to oxygen plasma.

For example, as the flattening layer 2, a resist (AZ-
1350J) is used, and two-layer structure resists using polydimethylsiloxane, a copolymer of trimethylsilylstyrene and chloromethylstyrene, chloromethylated polydiphenylsiloxane, etc. as the resist layer 3 are also known.

However, all the two-layer structure resists known so far are negative type, and positive type resists are not known.

(d) Object of the invention The object of the invention is to provide a method for forming a positive pattern with a large aspect ratio on a substrate with large steps.

(e) Structure of the Invention The purpose of the present invention is to form a positive resist pattern with a large aspect ratio by coating an electron beam resist on a substrate having significant irregularities.
After coating the substrate to be processed with a resin layer to flatten the unevenness, a resist made of a mixture of a crosslinkable methacrylic acid ester polymer and a phenyl silicone resin is coated on the resin layer to form a two-layer structure. The method is characterized in that a resist layer of the structure is formed, a window is opened in the upper resist layer by selective exposure to an electron beam and a development process, and then the lower resin layer is etched with oxygen plasma using the upper resist layer as a mask. This can be achieved by a method of forming a positive resist pattern.

That is, the present invention selects a phenyl silicone resin that is difficult to crosslink thermally and with energy beams such as electron beams and It provides etching properties.

In addition, the crosslinkable methacrylic acid resist has the effect of trapping the silicone resin added during pre-baking (heating) to form three-dimensional crosslinks of acid anhydrides into the intermolecular crosslinks and preventing them from dissolving. The silicone resin added can be dissolved for the first time by cutting the main chain of the resist and the crosslinks of the acid anhydride by exposure to ionizing radiation such as X-rays and X-rays.

Therefore, as shown in FIG. 1B, even if the resist layer 3 is selectively exposed to an electron beam 5, developed to open a window 4, and then etched entirely with oxygen plasma, the resist layer 3 is Since the silicone resin is trapped in the etching layer, the etching rate is low, resulting in the formation of a positive pattern as shown in FIG.

(f) Example of the invention Photoresist AZ-1350J manufactured by Shipley was coated on a silicon wafer and heated at 200° C. for 1 hour.

At this time, the film thickness is adjusted to 1.5 μm after heating. On top of this, a copolymer of methyl methacrylate (95 mol%) and methacrylic acid (5 mol%) (weight average molecular weight Mw = 2.0 × 10 ⁵ , dispersity 2.0) and methyl methacrylate (97 mol%) and methacrylic acid were added. acid (2.5 mol%) and methacrylic acid chloride (0.5
A hydrolyzed condensation polymer of trichlorophenylsilane (partially ladder phenyl silicone) is formed by a crosslinkable resist formed by mixing equal amounts of a terpolymer (w=2.0×10 ⁵ , dispersity 2.0) with resin,
Mw, 1.5×10 ³ , dispersity 1.5) was added in an amount of 25% by weight,
0.6 μm of resist solution dissolved in cyclohexanone
and heated at 155°C for 15 minutes.

After patterning this with an electron beam exposure dose of 40 μC/cm ² , it was immersed in methyl isobutyl ketone for 3 minutes, and then rinsed with isopropyl alcohol for 30 seconds and developed.

Next, a parallel plate dry etching device was used with an oxygen gas pressure of 0.1 Torr, a flow rate of 200 ml/min, and an RF power of 0.22 W/min.
The pattern of the resist layer 3 was transferred to the flattening layer 2 by etching for 13 minutes under the condition of cm ² .

Through this manufacturing process, we were able to form a 1.0 μm line and space pattern.

When forming a positive pattern using the above method, it is best to add silicone resin in an amount of 10 to 40% by weight; if it is less than 10% by weight, the resistance to oxygen plasma will be insufficient, while if it is more than 40% by weight, the sensitivity of the resist will decrease. descend.

(g) Effects of the Invention As described above, the present invention provides a method for forming a positive resist pattern with a high aspect ratio on a substrate to be processed with large steps, and can efficiently form a fine pattern.

[Brief explanation of drawings]

FIGS. 1A to 1C are cross-sectional views illustrating a method for forming a two-layer positive pattern according to the present invention. In the figure, 1 is a substrate to be processed, 2 is a flattening layer,
3, the resist layer 4 is a window opening, and 5 is an electron beam.

Claims (1)

[Claims] 1. When forming a positive resist pattern with a large aspect ratio by coating an electron beam resist on a substrate to be processed that has significant unevenness, after coating the substrate with a resin layer to flatten the unevenness, A resist made of a mixture of a crosslinkable methacrylic acid ester polymer and a phenyl silicone resin is coated on the resin layer to form a resist layer with a two-layer structure, and the upper resist is formed by selective exposure to an electron beam and development treatment. A method for forming a positive resist pattern, which comprises opening a window in the layer, and then etching the lower resin layer using oxygen plasma using the upper resist layer as a mask.