JPS61236125A - Dry-etching process - Google Patents

Abstract

PURPOSE:To prevent the etching rate from deteriorating while reducing any side etching by a method wherein a gas contributing to etching process as well as another gas contributing to forming a sidewall protecting film are jointly used. CONSTITUTION:A gas A led to a microwave plasma producing chamber 2 through a lead pipe 1 is excited by a magnetic field meeting the ECR requirements set up by microwave led by a waveguide 3 and coils 4 inside the plasma producing chamber 2 to produce ion and neutral radical. If the magnetic force line passing through the producing chamber 2 is led to pass a substrate 6, an ion stream 16 is carried to the substrate 6 together with the neutral radical as shown by arrow mark 16 to start etching reaction. On the other hand, another gas B contributing to forming a sidewall protecting film is led to a microwave plasma producing chamber 12 through another lead pipe 11. In such a constitution, if the magnetic force line formed by the coils 4 and the other coils 14 is combination with one another is kept not passing oven the wafer 6, an ion stream 17 is deflected from the substrate 6 carrying the neutral radical only to the substrate 6 to form the sidewall protecting film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an etching process, and particularly to a dry etching apparatus that prevents side etching and is suitable for highly accurate etching.

[Background of the invention]

Dry etching equipment generally uses gas to etch away unnecessary portions of the wafer surface. As the density of semiconductor devices increases, improvements in dimensional accuracy and faster processing are required. Particularly when etching gate electrodes with strict dimensional accuracy, or when etching deep grooves or deep holes with large processing depths, side etching under the resist occurs, which is a problem.

Side etch refers to etching under the resist that is not desired (・
This refers to a phenomenon in which etching goes around the pattern of a resist or the like to reach an area. It is said that the main influences are the gas pressure of the etching atmosphere and the substances generated during the etching process.

On the other hand, in the etching process, it is known that carbon C and nitrogen N react with the silicon substrate to form a film that is difficult to etch, and the resist decomposes during etching and some of it adheres to the sidewalls of the pattern. It is known that it helps prevent side etch. In the past, these side etch prevention layers were accidentally produced as a by-product of etching, and therefore they adhered to the bottom surface to be etched, resulting in problems such as lowering the etching rate.

Specifically, if a CVD apparatus such as that disclosed in Japanese Patent Application Laid-Open No. 155535/1984 is used for etching, the following problem will occur.

That is, in this apparatus, etching gas A is introduced into a plasma generation chamber and excited to generate ions and neutral radicals. However, the etching gas B diffuses into the plasma A from the second gas introduction system and is only indirectly excited by the plasma A, so that it is difficult to turn into plasma. Also,
Even if the gas B is turned into plasma, both the ions and neutral radicals therein will be incident on the wafer.

The ions of gas B, which has a deposition effect, enter the wafer perpendicularly through the ion sheath and are deposited mainly on the bottom of the processed surface, so they not only do not contribute to sidewall protection, but also increase (reduce) the etching rate. turn into.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and method for reducing side etching in dry etching techniques without causing a decrease in etching rate.

[Summary of the invention]

The present invention is characterized in that etching is performed by supplying only the plasma of gas A, which contributes to etching, and the neutral radicals of gas B, which contributes to the formation of a pattern sidewall protective film, to the substrate.

That is, the structure is such that etching is performed while actively forming a sidewall protective film to prevent side etching. For this purpose, a gas that contributes to etching and a gas that contributes to forming a sidewall protective film are used simultaneously.

When etching silicon, a gas A with an etching effect (e.g. 5F4) is excited to generate ions and neutral radicals, and these are incident on the wafer, and at the same time a gas B with a deposition effect (e.g. C containing carbon
F,, N,, NE(.

etc.) to generate neutral radicals, which form a protective film on the sidewalls.

Hereinafter, the present invention will be explained with reference to the cool-down environment.

It is desirable that the gas B contributing to the formation of the sidewall a-retaining film is isotropically incident on the substrate. In other words, it needs to be a neutral radical, not an ion.

If gas B ions are also supplied to the substrate, the ions will be accelerated in the sheath near the substrate by the substrate bias voltage normally applied to perform anisotropic etching, and will be perpendicularly incident on the substrate. It is. Therefore, the incident flux of gas B ions and neutral radicals that contribute to film formation to the bottom surface of the pattern becomes larger than the incident flux to the sidewalls, and an unnecessary film is formed on the bottom surface of the pattern, reducing the etching rate. It will lead to it.

Further, it is preferable that the etching gas A is ions and is incident perpendicularly to the substrate by a sheath electric field. In actual etching, both ions and neutral radicals contribute to the reaction, so the neutral radicals of gas A are also necessary to improve the etching rate.

Considering the above points, it is important to prevent the ions of gas B from reaching the substrate in order to perform highly accurate etching while protecting the pattern sidewalls without significantly reducing the etching rate.

This method uses the movement of charged particles such as ions along magnetic lines of force. That is, gas A and gas B are excited separately, so that the magnetic lines of force passing through the plasma generating part of gas A are brought toward the substrate, and the lines of magnetic force passing through the plasma generating part of gas B are removed from the substrate. However, if the radicals generated in the plasma generation chamber of gas B were ionized during transport to the substrate, there would be no meaning in separating them, but for example, at a pressure of 10-'Tart.

If the degree of ionization is 1% and the electron density is 10'7cd, the mean free path between the collision between the neutral particles and the electrons, which ionizes the neutral particles, is approximately 1 m, and the distance between the plasma generation chamber and the wafer is approximately 1 m. Since it is sufficiently long compared to the distance α1m, the probability that radicals of gas B will be ionized is extremely low.

Furthermore, if the gas introduced into the plasma generation chamber B immediately enters the plasma generation chamber A due to diffusion, the grand prize ions B will be generated in the plasma generation chamber, and the effect of the present invention will be diminished.

Therefore, gas B can be prevented from entering plasma generation chamber A by providing a partition wall between the two plasma generation chambers.

As a means of separating ions B from the plasma of gas B and preventing them from reaching the substrate, a grid with a positive potential is provided between the plasma generation chamber and the substrate, and the ions with a positive charge are repelled by the grid and are not allowed to pass through the grid. can be mentioned.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows one embodiment of the plasma etching apparatus of the present invention. In the figure, a gas A contributing to etching is introduced into a microwave plasma generation chamber 2 through an introduction pipe 1. As shown in FIG.

The gas person uses the waveguide 113 inside the plasma generation chamber 2.
It is excited by the introduced microwave and the magnetic field created by the coil 4 that satisfies the ECR conditions, and ions and neutral radicals are generated.

Both ions and neutral radicals diffuse into the sample chamber 5, but the diffusion of ions is restricted in the direction of the magnetic field created by the coils 4 and 14. If the lines of magnetic force passing through the generation chamber 2 are made to pass through the substrate 6, the ions are transported together with the neutral radicals to the substrate 6, as shown by the flow 16, and an etching reaction occurs.

On the other hand, the gas B contributing to the formation of the sidewall protective film is introduced into the inlet pipe 11
It is guided to the microwave plasma generation chamber 12 through the microwave plasma generation chamber 12. Here, as in the case of a gas person, ions and neutral radicals are generated by being excited by the microwave guided from the waveguide 15 and the magnetic field created by the coil 14 that satisfies the ECR conditions, and they flow into the sample chamber 5. Spread. Here, if the magnetic lines of force created by the sweet acid of the coils 4 and 14 are prevented from going back up the Ueno S6, the ion flow 17 will be diverted from the substrate 6, and only neutral radicals will be transported onto the substrate 6, and the side wall A protective layer grows. The partition wall 15 prevents neutral particles of the gas B from entering the plasma generation chamber 2 before entering the substrate.

Furthermore, by changing the output of the microwave introduced from the waveguide 13, the neutral radical concentration of the gas B can be changed, so it is possible to obtain the growth rate of the side wall S glands relative to the etching rate of the bottom part. .

Another example is shown in Figure i@2. The gas that contributes to etching passes through the introduction pipe 1 to the micro temporary plasma generation chamber 2.
guided by. Inside the plasma generation chamber 2, a magnetic field that satisfies the ECR conditions is created by a coil 4, and the gas is turned into plasma at a pressure of 10-4 to 10-Tart 8 degrees. Ions of gas A diffuse at thermal speed along the lines of magnetic force diverging toward the substrate 6, as shown by the arrow 16, and neutral radicals diffuse regardless of the lines of magnetic force, both of which are directed toward the substrate 6. reach. On the other hand, gas B, which mainly contributes to the formation of the sidewall protective film, is guided to the annular upper electrode 20 through the introduction tube 11 and is blown out from a small hole (not shown) provided in the electrode. Upper electrode 20 and lower electrode 21
A tube frequency power is applied to the coil 22 and the core 23.
As a result, a magnetic field is generated below the upper electrode 20. Due to the interaction of the electric field E and the magnetic field B, a plasma 24 is generated under the upper electrode, similar to the principle of a normal planar magnetron. In this plasma, the ions of gas B form an annular plasma 24 due to the EXB drift caused by the magnetic field B.
Since the neutral radicals are confined in the region of , only neutral radicals reach the wafer through thermal diffusion.

In this embodiment as well, by adjusting the microwave power for exciting gas A and the high frequency power for exciting gas B, it is possible to form an optimal sidewall protective film without slowing down the vertical etching speed.

Depending on the pressure condition, for example, 10-2 to 1o-1 Torr
In r, a magnetron is not required to excite the gas B since plasma is generated by a normal discharge. In this case, the ions of the dregs B will not cross this magnetic field and reach the wafer due to the magnetic field created by the coil 4, so that the original objective can be achieved.

Another embodiment is shown in FIG. In this embodiment, the plasma generation chamber 12 for gas B is arranged concentrically surrounding the outside of the plasma generation chamber 2 for gas A. As in the previous embodiment, gases A and B are turned into plasma. Since the substrate 6 is located below the plasma generation chamber 2, the ions of gas A that are diffused along the magnetic field by the coil 4 reach the substrate 6, but the ions of gas B are directed outward and do not reach the substrate 6. not reached.

Yet another embodiment is shown in FIG. The gas A is turned into plasma in the plasma generation chamber 2 and diffused toward the substrate 6 along the magnetic field created by the coil 4 .

On the other hand, gas B is turned into plasma in the plasma generation chamber 12, but because of the positive potential grid 40 made of St properties provided at the exit of the generation chamber 12, positive ions are repelled and do not pass through the grid 40. Therefore, the ions and neutral radicals of A and the neutral radicals of B reach the substrate 6.

Another embodiment is shown in FIG. In this embodiment, light is used as a means for generating only neutral radicals from gas B, and the activation efficiency of gas B is taken into consideration. For example, in the case of CF, the dissociation energy of F is about 5 eV, while the ionization energy is about 10 eV, so at a wavelength of 200
Ultraviolet light around nx will meet the purpose.

The gas is turned into plasma in the plasma generation chamber 2 and diffused toward the substrate 6 along the magnetic field created by the coil 4. On the other hand, gas B is supplied near the substrate 6. Light 5o having a wavelength that dissociates gas B to create neutral radicals but does not ionize it is irradiated onto the substrate surface through the glass window 51 to create neutral radicals of gas B.

〔Effect of the invention〕

According to the present invention, there is an effect that side etching can be prevented without greatly reducing the vertical etching speed, and high precision processing can be performed.

Furthermore, the excitation rate of gas B can be adjusted to tA to obtain an optimal sidewall protection effect.

[Brief explanation of drawings]

Figs. 1 and 4 are plan views of different embodiments of the present invention, Figs. 2 and 3 are llr plane views of different embodiments, taking into account the flow of gas, and Fig. 5 is a plan view of different embodiments of the present invention, and Fig. 5 is a plan view of different embodiments of the present invention. FIG. 1... Gas introduction pipe, 2... Plasma generation chamber,
3... Waveguide, 4... Coil, 5...
Sample chamber, 6... Substrate, 11... Gas introduction tube, 12... Plasma generation chamber, 13... Waveguide,
14... Coil, 15... Partition wall, 16... Flow of etching gas ions, 17... Flow of side wall protective film forming gas ions, 20... Upper electrode,
21... Lower electrode, 22... Coil, 23.
...Core, 24...Plasma.

Claims (1)

[Claims] 1. Introducing a gas that contributes to etching into a vacuum apparatus, exciting it to a plasma state, and guiding it to a target sample, and introducing a gas that adheres to the target sample and forms a substance that hinders etching. A dry etching method in which the target is guided into an activated state and selectively etched. 2. In the dry etching method according to claim 1, the hindering substance is introduced from a direction substantially perpendicular to the surface where etching is not desired, and the gas contributing to the etching is introduced from a direction along the etching direction. A dry etching method characterized by: 3. The dry etching method according to claim 1, wherein the inhibiting substance is activated by a light wave having excitation energy that does not ionize and has a necessary energy depending on the substance. Method.