JPH0834201B2 - Etching method and apparatus thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an etching method and apparatus for microfabrication of electronic parts such as semiconductor integrated circuits, and particularly to prevent breakdown voltage deterioration of an insulating film constituting a sample. Etching method and apparatus suitable for

[Conventional technology]

In recent years, a plasma etching method using glow discharge plasma of low-pressure gas has been widely used to form a fine pattern of a semiconductor integrated circuit or the like. This method utilizes the property that ions generated in plasma enter the sample surface perpendicularly, and is a method of highly accurate etching processing in accordance with the etching mask dimensions. Technology ”Industrial Books 1980 (English translation of'Applications of Plasma Processes to VLSI Technol
ogy'John Wiley & Sons 1985). In either method, the sample to be etched comes into contact with the plasma, and charged particles (ions and electrons) enter the sample surface from the plasma. Since the mobility of electrons is higher than the mobility of ions, electrons accumulate on the sample surface and are negatively charged with respect to the plasma potential. As a result, the ion and electron flux incident on the sample becomes the same. Usually, the sample surface potential is about -20 V with respect to the plasma potential.In a semiconductor integrated circuit having a thin insulating film in its internal structure, a conductor portion or a semiconductor corresponding to one electrode with the insulating film separated is used. When the potential of the portion is different from the surface potential of the sample, the insulation film is broken or deteriorated. Also,
When the surface material to be etched is a conductor, when a sample is placed in a high frequency electric field for generating plasma, an induced electric field is generated in the conductor and an eddy current flows. Also in this case, when the conductor faces the other conductor across the thin insulating film, the insulating film may be broken or deteriorated.

As described above, in plasma etching, an electric field due to the accumulation of incident charged particles and high frequency induction is applied to the insulating film, and it is presumed that these cause destruction or deterioration of the insulating film. This point has not been sufficiently taken into consideration in the conventional plasma etching apparatus, and the insulating film becomes thinner as the integrated circuit becomes more highly integrated. For example, when the gate insulating film thickness of a Si MOS transistor becomes about 100 Å, The withstand voltage is only about 10 V, and it is feared that the conventional plasma treatment deteriorates the insulating film.

[Problems to be solved by the invention]

It is an object of the present invention to provide an etching method which does not accumulate electric charges on the surface or induce an electric field associated with the conventional plasma treatment as described above. The charge accumulation and the induction electric field are caused by injecting charged particles into the sample or by arranging the sample in the high frequency electric field, and therefore it is necessary to completely eliminate them for the above purpose.

As recently discussed in Bakiyuam, 34 (1984) p. 259 to 261 (Vacuum, 34 (1984) pp259-261), particles extracted from a particle source called a saddle field source are Almost all of them are fast neutral particles, and surface treatment methods such as etching using them have been proposed.However, this fast neutral particle source cannot control the energy and flux independently, Has the disadvantage that only relatively high energies above about 1 KeV can be obtained.

Therefore, a more limited object of the present invention is to generate fast neutral particles of desired energy and impinge them on the sample surface to achieve the desired fine etching.

[Means for solving problems]

The above object is achieved by making the particles incident on the surface of the sample only electrically neutral particles having a relatively low energy and not exposing the sample to a high frequency electric field. In the field of etching processing of a fine pattern, which is an application field of the present invention, since high-precision processing through an etching mask is required, at least a part of particles incident on the sample has a certain directionality (for example, perpendicular) to the sample surface. It is necessary to hold the beam to enter. Therefore, in the present invention, the ions formed by the ion source are extracted by an electric field to be accelerated to a desired energy, and charge exchange with gas molecules, neutralization of ions on the solid surface, recombination of electrons with ions After neutralizing high-speed particles by a method such as neutralization, the particles are made incident at a desired angle on the sample surface. At the same time, Cl ₂ , HCl, BCl ₃ , CCl ₄ ,
A halide gas such as XeF ₂ , F ₂ and CClF ₃ is supplied. These gas molecules are adsorbed on the surface of the sample such as Si, GaAs, Al, W, etc. When neutral high speed particles enter, the etching reaction proceeds due to the energy.

[Action]

The reactive gas of the halide supplied to the sample surface is only adsorbed on the sample surface, and the etching reaction hardly progresses by itself, but the etching progresses at a considerable speed only by injecting neutral high-speed particles. To do.

Further, when neutral fast particles are incident on the sample surface, secondary electrons are generally emitted from the surface and positive charges are accumulated on the sample surface. At this time, the secondary electron emission coefficient is the same energy, ions of the same particle. Is smaller than that in the case of incident light, the surface charging is smaller than that in the case of ion injection. Further, when the incident energy of the neutral high-speed particles is about 1 KeV or less, secondary electrons are hardly emitted from the surface, and accordingly, the surface is hardly charged. Therefore, in order to achieve the object of the present invention, the energy of the neutral high-speed particles incident on the sample surface should be 1 KeV or less, and more preferably 500 eV or less.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The Ar ⁺ ions generated by the ion source 1 were accelerated by the extraction electrode 2 to an extraction energy of 450 eV. A vacuum chamber 4 having a length of about 50 cm is provided in front of the ion source 1, and an etching sample 5 is arranged so as to face the ion source 1. Sample 5 has a thickness of about 100 on the Si substrate.
A Å SiO ₂ film is formed, polycrystalline Si is deposited on it to a thickness of 3000 Å, and a photoresist pattern is further formed on it. Cl ₂ is supplied to the vacuum chamber 4 from the gas supply hole 6 and, at the same time, exhausted by the turbo molecular pump 7,
The Cl ₂ pressure was kept at 5 × 10 ^-4 Torr. A pair of deflecting plates 8 is placed in the vacuum chamber 4, and each electrode has + 350V, -350V.
DC voltage was applied. Ar ⁺ extracted from the ion source 1
Most of the ions are neutralized by the charge exchange reaction with Cl ₂ on the way to the sample 5, but there are Ar ⁺ ions remaining without being neutralized. The deflector 8 is a means for deflecting the residual ions so that they do not enter the sample.

Under the above conditions, the flux of Ar neutral fast atoms is 5 × 10.
^{At 14} / cm ² · sec, the etching speed of polycrystalline Si is about 100.
It was 0Å / min. After etching, the polycrystalline Si electrode and substrate S
A voltage was applied between i and the insulation breakdown voltage of the SiO ₂ film was evaluated, but the breakdown voltage was not deteriorated.

〔The invention's effect〕

According to the present invention, it is possible to prevent the breakdown voltage of the thin insulating film from being deteriorated during the etching process, so that it is possible to manufacture a highly reliable semiconductor integrated circuit or the like with a high yield.
This effect is particularly large when the energy of the neutral fast particles entering the sample during the etching process is reduced to about 500 eV or less as described above, and the thin insulation often seen when etching is performed by ordinary plasma etching. Almost no dielectric breakdown of the film is seen.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an apparatus according to an embodiment of the present invention. 1 ... Ion source, 2 ... Ion extraction electrode, 3 ... Ion source filament, 4 ... Vacuum chamber, 5 ... Etching sample, 6 ... Gas supply hole, 7 ... Turbo molecular pump, 8
...... A deflector.

Continuation of the front page (56) References JP 61-136229 (JP, A) JP 62-185324 (JP, A) JP 62-98731 (JP, A) JP 59-225525 (JP , A) JP 59-139539 (JP, A) Actually developed 55-99145 (JP, U)

Claims (7)

[Claims] 1. An etching method, characterized in that neutral fast particles obtained by neutralizing ions accelerated to an energy of 1 KeV or less and a reactive gas containing halogen as a constituent atom are supplied to a sample surface. . 2. The etching method according to claim 1, wherein the reactive gas can be adsorbed on the sample surface. 3. An ion source for producing ions, an ion accelerating means for accelerating the ions produced by the ion source to an energy of 1 KeV or less, and neutralizing the ions accelerated by the ion accelerating means. Neutralization means for generating high-speed particles, neutral high-speed particle supply means for making the neutral high-speed particles generated by the neutralization means incident on the sample surface to be etched, and reactivity containing halogen as a constituent atom An etching apparatus comprising: a reactive gas supply means for supplying a gas to the surface of the sample. 4. The neutral high speed particle supplying means includes an ion deflecting means for deflecting the ions remaining in the neutral high speed particles so as not to enter the sample surface. The etching device according to claim 3. 5. The etching device according to claim 3, wherein the neutralizing means neutralizes ions by charge exchange with gas molecules. 6. The etching apparatus according to claim 3, wherein the neutralizing means neutralizes the ions by neutralizing the ions on the solid surface. 7. The etching apparatus according to claim 3, wherein the neutralizing means neutralizes ions by recombination with electrons.