JPS60263145A - Formation of positive type resist pattern - Google Patents

Abstract

PURPOSE:To form a positive type resist pattern high in aspect ratio on the substrate high in level difference to be processed by etching the lower resist layer through the resist layer made of a mixture of a bridgeable methacrylate polymer and a phenyl silicone resin as a mask. CONSTITUTION:A flattened layer 2 is formed on the roughened substrate 1 to be processed. The resist layer 3 is formed on the layer 2 by coating it with a resist soln. prepared by mixing a copolymer of methyl methacrylate and methacrylic acid with a terpolymer of methyl methacrylate, methacrylic acid, and methacryloyl chloride, in amts. equal to each other, adding a hydrolyzed polycondensate of trichlorophenylsilane (partial ladder phenyl silicone resin) to the obtained bridgeable resist in an amt. of 25wt%, and dissolving them in cyclohexanone. The resist layer 3 is selectively exposed to electron beams, developed to open a window 4, and etched with oxygen plasma to transfer the pattern of the resist layer 3 to the flattened layer 2.

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) Technology background IC-? ) Unit elements of electronic circuit elements, as typified by semiconductor elements such as LSI, are becoming smaller and more integrated, and various patterns, including conductor patterns, are becoming extremely fine. There is.

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.

Photo-etching technology uses photoresist to be coated on the substrate to be processed using a method such as a spin cord, and selectively exposed to ultraviolet light through a mask, making use of the difference in solubility of the light irradiated areas to the developing solution. 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 having 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 the electron beam varies depending on the accelerating voltage, but is 0.1
Since the wavelength is much shorter than that of a human, it is also possible to form a pattern with a width of 0.1μ.

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, wiring patterns are multilayered.

For example, in the case of semiconductors, a thin film of aluminum (AI) or poly-Si is formed on a silicon (Si) single-crystal substrate, a conductor pattern is created by performing etching or other processing on this, and then phosphosilicate glass (abbreviated as PSG) and silicon dioxide (
A Si 02 ) layer 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 R and IB), 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 on top by a method such as a spin code 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 etching of the substrate to be processed is completed. Therefore, pattern breakage is likely to occur, and dimensional accuracy is not achieved.

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

1 (A) to (C) show this method, in which a planarization layer 2 is formed by thickly coating an organic resin on an uneven substrate 1, and a dry resistant layer 2 is formed on this. A resist layer 3 with excellent etching properties is formed, the upper resist layer 3 is selectively exposed and developed to form a window 4, and then dry etching is performed using the upper resist layer 3 as a mask to etch the substrate 1 to be processed. A pattern is formed by processing the material.

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 manufactured by Sibley) made of polyimide resin or Talesol novolanque resin and a naphthoquinone diazide derivative is used, and as the resist layer 3, polydimethylsiloxane, trimethylsilylstyrene, and chloromethylstyrene are used. Two-layer structure resists using copolymers with chloromethylated polydiphenylsiloxane and chloromethylated polydiphenylsiloxane are 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 An object of the present 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 coat a substrate with remarkable unevenness with an electron beam resist to form a positive resist pattern with a large aspect ratio. After coating to flatten the unevenness, a crosslinkable methacrylic acid ester polymer and phenyl silicone are applied on the resin layer.
, a resist made of a mixture with a resin is coated to form a resist layer with a two-layer structure, and a window is opened in the upper resist layer by selective exposure to an electron beam and development treatment, and then the upper resist layer is used as a mask. This can be achieved by a method for forming a positive resist pattern characterized by etching the underlying resin layer with oxygen plasma.

That is, the present invention selects a phenyl silicone resin that is difficult to crosslink thermally or with energy beams such as electron beams and X-rays, and adds it to a thermally crosslinkable methacrylic acid ester resist to improve dry etching resistance against oxygen plasma. It is something that gives sex.

In addition, cross-linked methacrylic acid resist is pre-baked (heated).
It has the effect of trapping the silicone resin added when forming three-dimensional crosslinks of acid anhydrides in the intermolecular crosslinks and preventing them from dissolving, and the resist is removed by exposure to ionizing radiation such as electron beams and X-rays. By cutting the main chain and acid anhydride crosslinks, the silicone resin added for the first time can be dissolved.

Therefore, even if the resist layer 3 is selectively exposed to an electron beam 5 and developed to form a window 4, as shown in FIG. 1(B), the entire surface is etched with oxygen plasma. Since the silicone resin is trapped in 3, the etching rate is low and a positive pattern as shown in FIG. 3(C) is formed.

(f) Examples of the invention Photoresist AZ-1350J manufactured by Sibley Co., Ltd. The solution was applied onto a wafer and heated at 200°C for 1 hour.

At this time, the film thickness is adjusted so that it becomes a 1.5 μm mist after heating. On top of this, a copolymer of methyl methacrylate (95 mol%) and methyl methacrylate (5 mol%) (weight average molecular weight M
Tsuba-2, OXIO', dispersity 2.0) and a terpolymer of methyl methacrylate (97 mol%), methacrylic M (2.5 mol%) and methacrylic acid chloride (0.5 mol%) (M-=2.OXIO3, dispersity 2.0) in a crosslinkable resist formed by mixing equal amounts of trichlorophenyl? Ran's hydrolyzed condensation polymer (partial ladder phenyl silicone resin, w = 1.5 XIO3, dispersity 1
．． A resist solution containing 25% by weight of 5) dissolved in cyclohexanone was applied to a thickness of 0.6 μm in a pan and heated at 155° C. for 15 minutes.

After patterning this with an electron beam exposure dose of 40 μC/cd, 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 type dry etching device was used to reduce the oxygen gas pressure to 0.
1Torr, flow rate 200m1/sin, RF power 0
．． The pattern of the resist layer 3 was transferred to the flattening layer 2 by etching for 13 minutes at 22 W/d.

Through this manufacturing process, a line and space pattern of 1.0 μm could be formed.

In addition, when forming a positive pattern by the above method, the amount of silicone resin added is preferably 10 to 40% by weight.
If it is less than 40% by weight, resistance to oxygen plasma will be insufficient, while if it is more than 40% by weight, the sensitivity of the resist will decrease.

(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 fine patterns.

[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 is a resist layer 4 having a window opening, and 5 is an electron beam.

Claims (1)

[Claims] 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 irregularities, a resin layer is coated on the substrate to be processed to flatten the irregularities. 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 resist layer, and the upper resist layer 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 and then etching a lower resin layer using oxygen plasma using the upper resist layer as a mask.