JPS63148637A - Dry etching - Google Patents

Abstract

PURPOSE:To improve highly selective etching properties for a foundation material by a method wherein etching gas is composed of a gas group which mainly etches metal oxide in a sample and a gas group which mainly forms deposited metal on the foundation material of the sample. CONSTITUTION:A gas plasma is generated under a reduced pressure and a sample is etched by utilizing the plasma. The gas is composed of a gas A group which mainly etches metal oxide in the sample and a gas B group which mainly forms deposited metal on the foundation material of the sample. With this constitution, a selection ratio can be improved to the level of the selection ratio required in etching of a submicron device by the effect of the deposited metal on the foundation material produced by a reducing reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry etching method, and more particularly to a dry etching method that has excellent selective etching properties for underlying materials of samples such as semiconductor device substrates.

[Conventional technology]

With the miniaturization of semiconductor devices, it is strongly desired that the dry etching used for processing the devices be improved in not only precision etching properties but also highly selective etching properties.

In particular, dry etching of metal oxide films in submicron devices with dimensions of less than 1 μm requires a high selectivity (approximately 30 or more) to the underlying material (ratio of etching speed of the metal oxide film to the underlying material). There is.

In order to improve the selectivity, for example, a technique has been proposed to reduce the strong etching species on the underlying material. For example, in the hat of Japanese Patent Publication No. 59-46094, materials such as molybdenum, tungsten, and silicon that absorb fluorine radicals, which are strong etching species for silicon, which is the underlying material, are constructed in an etching device, and the materials and fluorine radicals are A technique has been disclosed in which the amount of fluorine radicals is reduced by a reaction to improve the selectivity of silicon oxide, which is a metal oxide film, to silicon, which is a base material.

In addition, an organic film is deposited on the base material using a mixed gas of a gas that etches the metal oxide film and a gas that has the effect of depositing an organic film as an etching gas, thereby suppressing the etching of the base material. Recently, techniques to improve the selectivity have been widely adopted. For example,
In the mixed gas of C2Fs + CHF3, C2F6 is an etching gas for silicon oxide, which is a metal oxide film, and silicon, which is an underlying material, and CHF3 is a gas for depositing an organic film. CHFa deposits an organic film of hydrocarbons on silicon oxide and silicon, but the life of the film is short because oxygen, an etching product of silicon oxide, chemically reacts with the hydrocarbons and decomposes them into volatile substances. Etching of silicon oxide progresses.

On the other hand, the hydrocarbon film deposited on silicon has a long lifetime in the absence of oxygen, and the etching selectivity is improved by suppressing silicon etching. Such technology is, for example, "1 Semiconductor Plasma Process Technology", p. 229,
Disclosed in Sangyo Tosho (July 1982).

[Problem that the invention seeks to solve]

In the first conventional technique, since the etching species are also reduced during etching of the metal oxide, the etching rate of the metal oxide is suppressed to a low level, and there is a problem that a sufficient selectivity cannot be obtained. .

In addition, in the second conventional technique, the etching rate of the metal oxide is relatively high, and the selectivity is also to a certain extent (10 to 15
). However, the selectivity obtained with the second technique is still insufficient for etching submicron devices.

An object of the present invention is to provide a dry etching method that can improve the selectivity to the level required for etching submicron devices (approximately 30 or more).

[Means for solving problems]

The above object is to provide a dry etching method in which a gas is turned into plasma under reduced pressure and a sample is etched using the plasma, in which the gas is a gas that mainly etches metal oxides in the sample and the sample is etched. This is achieved by a method characterized in that the gas group B is mainly comprised of gas group B that causes metal deposits to be formed on the underlying material.

[For production]

In other words, in the gas group, the single-component gas region of a fluorine-containing compound is composed of multiple-component gases.

The following three types of gas are effective for gas people.

@l system...-NF3. SF.

@2 system: Compound containing fluorine and carbonic acid. 3rd system: Compound where part of the fluorine in the 2nd system is replaced with hydrogen or chlorine. Silicon oxide as a metal oxide film. An example will be chosen and explained below. These gas molecules collide with electrons in the plasma to dissociate and generate fluorine radicals and ions, and the fluorine radicals react with silicon oxide with the help of the ions, thereby etching the silicon oxide. Gas group A also etches the underlying material, silicon.

The following two systems of gas are effective for gas group B.

1st system・・・・W F6, MoF6 2nd system・
...A compound in which part of the fluorine in the first system is replaced with hydrogen or chlorine.

These gases deposit tungsten or molybdenum metals on silicon, but very little on silicon oxide. This is because silicon causes the reduction reaction of the following formula with respect to gas group B, whereas silicon oxide does not cause any reaction.

Gas group B
A metal substance is deposited on silicon by the above-mentioned reduction reaction. For this reason, the silicon is covered with metal deposits and etching does not proceed.

Note that tungsten and molybdenum are also etched by gas group A, but when the underlying material silicon is etched, metal objects are deposited, and as etching and deterioration are repeated, the metal film may grow large or the underlying material may be The material is not etched to a large extent. [Example] An example of the present invention will be described below with reference to FIGS. 181 to 2.

Figure m1 shows an example of an etching apparatus to which the present invention is applied, in which an etching chamber l houses an upper electrode 2 and a lower mold [j3] via an insulating member 4.5 having a sealing mechanism, and has an exhaust hole 6. The upper electrode 2 is connected to the high frequency die #7, the lower die &3 is grounded, and the semiconductor element substrate 9, which is a sample, is placed on its upper surface.

A mixed gas consisting of gas group A and gas group B, each having a controlled flow rate, is supplied from the lower surface of the upper electrode 2 and exhausted from the exhaust hole 6, and the etching chamber! A predetermined pressure is regulated inside. The introduced mixed gas is turned into plasma by high frequency discharge between the upper and lower electrodes, creates active species necessary for etching and deposition, and processes the semiconductor element substrate 8.

FIG. 2 shows data when a silicon oxide (8102) film was deposited on polycrystalline silicon by plasma CVD and etched using a photoresist as a mask.

When the WF6 concentration was 0%, the silicon oxide etching rate was 600 nm/min and the selectivity was 12.

The selectivity increases with the amount of WF6, and the decrease in etching rate is small, with an etching rate of 5 at 10% of WF6.
90 nm/min and a selectivity of 49 were obtained. This selectivity could be an improvement over the prior art in submicron devices. Note that when WFiO)all exceeds 20%, the selectivity tends to be saturated.

As gas group B, MOF6 and WF6. When using a compound in which part of the fluorine in MoF6 was replaced with hydrogen or chlorine, the selectivity improved as the concentration of the gas nB increased. Note that if the gases are in the three systems mentioned above, the effect of gas group B on the metal depositing action will be small.

The base material silicon may be single crystal silicon, polycrystalline silicon, or silicon in which impurities are diffused into both types of silicon.

The metal oxide film may be any film that can be etched by fluorine radicals or ions containing fluorine. Typical examples of metal oxides for which this patent is effective include silicon oxide, tantalum oxide, molybdenum oxide, tungsten oxide, and the like.

Furthermore, although the above explanation has been made regarding etching by high-frequency discharge, the action and effect of Structure 2 of the present invention do not change depending on the plasma generation method, and are also effective for plasma generated by microwaves or plasma generated by applying a magnetic field to microwaves. be.

〔Effect of the invention〕

According to the present invention, there is an effect that the selectivity can be improved to that required for etching submicron devices based on the reduction reaction (the action of depositing a metal substance on the underlying material).

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an etching apparatus to which the present invention is applied;
Figure 2 shows the etching rate of silicon oxide. FIG. 3 is a relationship diagram between selectivity and tungsten hexafluoride concentration.

Claims (1)

[Claims] 1. In a method of turning a gas into plasma under reduced pressure and etching a sample using the plasma, the gas includes a gas group A that mainly etches metal oxides in the sample; Gas group B that mainly forms metal deposits on the underlying material
A dry etching method comprising: 2. The dry etching method according to claim 1, wherein the metal oxide is etched with fluorine radicals or ions containing fluorine, and the material described below is silicon. 3. The dry etching method according to claim 2, wherein the gas group A is a single-component gas or a multi-component gas of a compound containing fluorine. 4. The dry etching method according to claim 2, wherein the gas group A includes a compound C containing at least carbon and fluorine. 5. The dry etching method according to claim 4, wherein the compound C is a compound in which a portion of fluorine is replaced with hydrogen or chlorine. 6. The dryer according to claim 2, wherein the gas group A is a mixed gas of a monocomponent gas or a multicomponent gas of a compound containing fluorine and a gas containing a compound C containing at least carbon and fluorine. Etching method. 7. The dry etching method according to claim 6, wherein the compound C is a compound in which a part of fluorine is replaced with hydrogen or chlorine. 8. The dry etching method according to claim 2, wherein the gas group B contains at least tungsten fluoride or molybdenum fluoride. 9. The dry etching method according to claim 8, wherein the tungsten fluoride is tungsten hexafluoride or has a molecular formula in which part of the fluorine in tungsten hexafluoride is replaced with hydrogen or chlorine. 10. The dry etching method according to claim 8, wherein the molybdenum fluoride is molybdenum hexafluoride or molybdenum hexafluoride having a molecular formula in which part of the fluorine is replaced with hydrogen or chlorine. 11. Claim 1, wherein the step of forming a metal deposit on the base material by the reduction reaction of the gas group B and the step of etching the metal deposit with the gas group A are repeatedly performed. dry etching method.