JPH05144782A - Dry etching method and its pretreatment device - Google Patents

Abstract

PURPOSE:To form a layer high in dry etching resistance, which includes bromine, at the surface of a photoresist mask, and raise the selection ratio with the photoresist effectively, by immersing the photoresist mask in solution while being exposed in the gas of bromine compound prior to dry etching. CONSTITUTION:A photoresist mask 13, which functions as a mask in dry etching, is made at the surface of a sample. And, a silicon substrate 10 is soaked in organic compound bromobenzene or bromoform and is let alone from several minutes to tens of minutes. Hereby, a layer 14, where carbon and bromine are coupled, is made at the surface of the photoresist pattern 13. A silicon substrate 10 being prepared this way is etched with an aluminum dry etcher. Since the layer 14, which contains bromine high in dry etching resistance, is made at the surface of this photoresist mask, the dry etching resistance of the photoresist can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for finely processing a thin film by plasma etching.

[0002]

2. Description of the Related Art Advances in high-density semiconductor integrated circuits are bringing about changes comparable to the industrial revolution. Higher densities have been realized by miniaturization of device dimensions, improvement of devices, and enlargement of chip size. The miniaturization of device dimensions has advanced to about the wavelength of light, and the use of excimer lasers and soft X-rays is being considered for lithography. Along with lithography, dry etching plays an important role in realizing fine patterns.

Dry etching is a processing method for removing an unnecessary portion of a thin film or a substrate by utilizing a chemical or physical reaction on a gas-solid phase surface by plasma, radicals, ions and the like. Reactive ion etching (RIE), the most widely used dry etching technology
Is that when a sample is exposed to a high-frequency discharge plasma of an appropriate gas, an unnecessary portion of the sample surface is removed by an etching reaction. Necessary portions are usually protected by the photoresist pattern used as a mask.

FIG. 4 is a schematic diagram showing a reactive ion etching apparatus using a conventional magnetron discharge. A reactive gas is introduced into the metallic chamber 1 through a gas controller 2, and an exhaust system 3 controls the reactive gas to an appropriate pressure. The upper part of chamber 1 is an anode
4 is provided, and a sample table 5 serving as a cathode is provided in the lower part. An RF power source 7 is connected to the sample stage 5 via an impedance matching circuit 6, and high frequency discharge can be generated between the sample stage 5 and the anode 4. A rotating magnetic field is applied to the chamber 1 by two pairs of AC electromagnets 8 facing each other, which are different in phase from each other, and are installed on the side surfaces to facilitate discharge in a high vacuum. The electrons have a cycloidal motion due to the applied magnetic field, so that the ionization efficiency is increased.

For aluminum etching, it is common to introduce a gas such as chlorine, silicon tetrachloride, chloroform or nitrogen into such an etching apparatus. A pressure of 20 to 50 Pa and an input power of about 200 to 500 W are used.

[0006]

To realize miniaturization, a high vacuum is applied to increase the anisotropy of the etching reaction, and
A high selection ratio with respect to the photoresist used as a mask is required. This is because if the selection ratio is small, the photoresist mask dimension and its shape change during etching, and accurate dimension transfer and vertical post-etching shape cannot be obtained. In addition, when the underlying step is large, the photoresist becomes thin in the part where the step is high, and therefore the pattern may disappear in that part if the selection ratio is small. Especially in the dry etching of the aluminum-based metal film used as the wiring of the LSI, it is difficult to obtain a high selection ratio with respect to the photoresist.

In order to realize a high selection ratio with respect to the photoresist, a so-called UV cure, which is a method of forming a difficult etching layer on the photoresist surface by irradiating the photoresist mask with ultraviolet rays while heating the photoresist mask to about 200 ° C., is performed. There is. However, the difficult-to-etch layer due to UV curing is limited to an extremely small surface of about 0.1 micron, and the selection ratio of photoresist to aluminum during etching was about 3 at most.

In view of the above problems, the present invention provides a dry etching method capable of increasing the selection ratio with respect to a photoresist.

[0009]

In order to solve the above problems, the dry etching method of the present invention is a method of exposing a photoresist mask to a gas of a bromine compound or immersing it in a solution prior to dry etching, The resist mask has a structure in which a layer containing bromine and having high dry etching resistance is formed on the surface of the resist mask.

[0010]

According to the present invention, a layer containing bromine is formed on the surface of the photoresist mask by the above-mentioned structure, and since this layer is a layer having high dry etching resistance, when this layer is used as a mask, the photo resist is effectively exposed. A high selection ratio with the resist will be obtained.

This is explained as follows. The photoresist contains carbon C because it is an organic substance.
When this is exposed or infiltrated in a compound containing bromine, a C-Br (carbon-bromine) bond is formed on the photoresist surface. Since the bromine compound is active, a layer having a C—Br bond grows thick with the time of exposure or infiltration.

On the other hand, the C--Br compound has a higher boiling point and is less likely to volatilize than the C--Cl compound, and therefore has a large dry etch resistance. A comparison of boiling points is shown in (Table 1).

[0013]

[Table 1]

Thus, since the layer containing bromine having high dry etching resistance is formed on the surface of the photoresist mask, the dry etching resistance of the photoresist is improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry etching method according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a manufacturing process for explaining a dry etching method according to an embodiment of the present invention.

First, as shown in FIG. 1A, the silicon substrate 1
0, an oxide film 11, and an aluminum film (Al-Si-Cu film and described below) 12 containing a small amount of Cu and silicon, a photoresist pattern 13 that functions as a mask during dry etching is formed on the sample surface.

In FIG. 1b, when the silicon substrate 10 is immersed in bromine-containing organic compound bromobenzene or bromoform and left for several minutes to several tens of minutes, a layer 14 in which carbon and bromine are combined is formed on the surface of the photoresist pattern 13. It

The silicon substrate 10 thus prepared
Was etched with an aluminum dry etcher as in the prior art (FIG. 1c). Gases such as chlorine, silicon tetrachloride, chloroform and nitrogen are introduced into the magnetron etching apparatus of FIG. 4, the pressure is 20 to 50 Pa, and the input power is 2
About 00 to 500 W was used.

Since the layer 14 containing bromine having high dry etching resistance is formed on the surface of the photoresist mask, the dry etching resistance of the photoresist is improved from 4 to 6. The dimensional accuracy was about 0.1 μm in the conventional example, but this method improves the selection ratio to 0.03 μm.
It becomes less than μm, and it can be used without any problem even if the design rule is less than 0.5 μm.

In the embodiment, the silicon substrate 10
Was dipped in bromobenzene or bromoform, but may of course be dipped in other bromine containing compounds. Also,
Instead of soaking in compounds containing bromine, they may be exposed to their high concentration of steam or atmosphere.

The dry etching pretreatment using such a bromine compound has a flow as shown in FIG. 2, and a heat treatment mechanism in a vapor of a bromine compound such as bromobenzene is provided in a part of the developing device in the photolithography process. By adding, the process time can be shortened. In FIG. 2, the processing time is shortened by performing the same processing as the post-baking step. FIG. 3 is a configuration diagram for explaining an embodiment of the dry etching pretreatment apparatus for performing the heat treatment in the bromine compound vapor of the present invention. After development and rinsing, the process is significantly performed by heating the photoresist-patterned silicon substrate 10 in a chamber 20 containing a bromine compound vapor such as bromobenzene to about 150 ° C. without pattern deformation. Is shortened to. It is desirable to control the vapor pressure of the bromine compound in order to enhance the reproducibility of the reaction between the bromine compound and the photoresist. This can be realized by a known method such as controlling the flow rate ratio of an inert gas such as nitrogen and a bromine compound gas.

As a dry etching pretreatment device for performing heat treatment in a bromine compound vapor, a conventional UV curing device may be used with an inlet for a bromine compound gas or the like and a vapor pressure control device added.

In the embodiment, the case where the present invention is applied to aluminum etching is shown, but it goes without saying that the present invention is also effective when applied to dry etching of other films.

[0025]

As described above, according to the present invention, the photoresist mask is exposed to the gas of the compound containing bromine or infiltrated in the solution to form a layer having high dry etching resistance on the surface of the photoresist mask. As a result, etching can be performed while maintaining a large selection ratio with respect to the material to be etched.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process for explaining a dry etching method according to an embodiment of the present invention.

FIG. 2 is a flow chart for explaining a sample processing flow when the dry etching pretreatment apparatus of the present invention is incorporated in a development line of a photolithography process.

FIG. 3 is a configuration diagram for explaining a dry etching pretreatment apparatus which is an embodiment of the present invention.

FIG. 4 is a configuration diagram for explaining a conventional dry etching apparatus and method.

[Explanation of symbols]

10 Silicon substrate 11 Oxide film 12 Aluminum film containing a small amount of Cu and silicon (Al
-Si-Cu film) 13 Photoresist pattern 14 Layer in which carbon and bromine are bonded 20 Chamber 21 Stage with temperature raising mechanism 22 Bromine compound vapor pressure controller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number in the agency FI Technical display location // H05H 1/46 9014-2G (72) Inventor Masayuki Endo 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Denki Sangyo Co., Ltd.

Claims (6)

[Claims] 1. A step of forming a photoresist mask on the surface of a material to be etched, and a step of exposing the photoresist mask to a gas of a compound containing bromine or immersing it in a solution to dry-etch resist the surface of the photoresist mask. And a step of forming a highly resistant layer, and a material to be etched is selectively etched using the photoresist mask. 2. The dry etching method according to claim 1, wherein the compound containing bromine is a bromine compound for the photoresist mask. 3. The dry etching method according to claim 2, wherein the bromine compound contains either bromobenzene or bromoform. 4. A chamber filled with a bromine compound vapor and a photoresist patterned sample for about 250.
A dry etching pretreatment device having a mechanism for raising the temperature to ° C or lower. 5. A development processing apparatus for at least a photolithography process is included.
The dry etching pretreatment apparatus described. 6. The dry etching pretreatment apparatus according to claim 4, further comprising a bromine compound vapor control mechanism.