JP2639158B2 - Etching method and etching apparatus - Google Patents

Description

The present invention relates to silicon, silicon oxide, silicon nitride, gallium arsenide, W alloy, Al alloy, Cu alloy, Fe-Si-Al alloy, NiFe alloy, diamond, and organic. The present invention relates to an etching method for forming a fine pattern on a compound or the like and an etching apparatus used for the method.

(Prior Art) Conventionally, as a typical method for etching a sample using atoms, ions, or molecules, ion beam etching has been put to practical use. It is, for example, L. David Bollinger: Solid State Technology, 1983
The etching is performed by using an apparatus as disclosed in page 99 of January, January, and its outline is as shown in FIG. Here, a method of etching a sample using an argon ion beam will be described with reference to FIG.
That is, in the ion source 13, the electrons 15 jumping out of the cathode 14 collide with the argon gas 11 supplied from the cylinder during the cyclotron motion by the magnet 16, and generate argon ions 12. The argon ion beam
The electron beam 12 is accelerated by the acceleration electrode 8 into the etching chamber 4 outside the ion source 13, and is irradiated on the sample 10 on the substrate 9 together with the electrons 18 emitted from the filament 6. Here, the argon ions 12 colliding with the sample 10 cause sputtering on the surface of the sample 10 to etch the sample 10.

(Problems to be Solved by the Invention) In recent years, in the conventional ion beam etching described above,
Since the base is irradiated with high-energy ions, HRDe
As disclosed in ppe et al., Solid State Electronics, Vol. 20, 1977, p. 51, radiation damage on the crystallinity of the material surface has become a problem. In the study of the present inventor, an electron beam diffraction of the surface was also performed after etching was performed at 5,000 mm by an argon ion beam irradiated on a single crystal quartz substrate having a diameter of 2 inches at an acceleration voltage of 1 kV and an ion current density of about 1 A / cm ^2. As a result, a damaged region having a maximum lattice defect density of 100 mm at the maximum was observed in the depth direction of the etched surface.

Therefore, in order to reduce the damage, it is conceivable to keep the acceleration voltage during ion beam etching low and irradiate the sample with high ions so as to have no energy. There is a problem that it cannot be obtained. In order to avoid this phenomenon, it is necessary to develop a device having a large number of ion sources as described above and capable of simultaneously irradiating a sample with a large number of ion beams. Not a target.

By the way, in the field of film formation, film formation using a metal cluster ion beam is performed. This is a technique for irradiating a substrate with a cluster beam to form a thin film of a cluster constituent material on the substrate. A cluster is a collection of many atoms or ions. Therefore, when a cluster is accelerated with a certain acceleration voltage, the retained kinetic energy per atom becomes smaller than that when a single atom is accelerated. Therefore, when a cluster ion beam is used for film formation, a high-quality film with few defects can be formed as compared with a case where a single ion is accelerated to form a film. The film formation method using these cluster ion beams is described in Toshinori Takagi: Applied Physics, Vol. 55,
No. 8, 1986, p. 746, but currently the application of cluster ion beams is limited to the field of film formation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of performing etching while reducing damage to a sample surface due to beam irradiation by using a cluster, and an apparatus used for the method.

(Means for Solving the Problems) The present invention provides an etching method for performing etching by supplying a highly reactive gas to a sample surface while supplying clusters to the sample surface. In order to realize the etching method, a cluster generating portion, an etching chamber portion including a vacuum exhaust mechanism for introducing a cluster generated by the cluster generating portion, a portion for ionizing the cluster, and a sample being ionized by the ionized cluster beam A substrate held in the accelerating electrode for accelerating the ionized cluster toward the substrate by an electric field, a collimator portion for converting the ionized cluster into a parallel beam, and a portion filled with a gas having reactivity with the sample, A portion for introducing a required amount of the reactive gas to a sample surface on a substrate in an etching chamber.

(Function) As described above, the kinetic energy per atom of the cluster is smaller than that of ions in the conventional ion beam etching. For example, when argon ions are accelerated at 1 kV, the kinetic energy possessed is about 1000 eV per atom (ion).
However, when a cluster is composed of, for example, 100 atoms and is monovalently ionized as a whole, 1 kV
Even if it is accelerated by the acceleration voltage, the kinetic energy per atom is about 1/100 of 10 eV, which is about 1/100 of 1000 eV in the case of the ion etching apparatus. Considering the initial process of etching, it is necessary to displace the outermost surface atoms of the sample from the original lattice position, but the energy required for this is about several eV of the interatomic bond energy. Although the energy is low, the amount of energy held by each atom is about 10 eV in consideration of the above example. Therefore,
By the collision of the clusters, the outermost surface atoms of the sample can be desorbed from the sample, and the etching can proceed. When the sample is irradiated with such a low-energy cluster ion beam, penetration into the sample is less likely to occur than when the high-energy ion beam is irradiated. Has the characteristic that it is not easily damaged. According to the study of the present inventor, a substrate on which silicon was epitaxially grown was etched with an argon cluster beam, and immediately after that, the in-situ evaluation of the crystallinity of the etched surface was performed by RHEED (reflection high-speed electron beam diffraction). It had high crystallinity almost as good as before. On the other hand, when the etching was performed with the argon ion beam, which is a conventional technique, the RHEED pattern became halo-shaped, indicating that the crystallinity was reduced. As described above, if the etching method using the cluster beam is used, the etching can be performed while maintaining the crystallinity of the sample surface, so that there is no need to perform a step of annealing or the like to recover the crystallinity after the etching, and the product is actually manufactured. In the case of manufacturing, the number of steps can be reduced, and cost and time can be saved. When the number of times of etching is large, the number of steps can be significantly reduced.

In addition to low damage, when a highly reactive gas is supplied on the sample surface simultaneously with the irradiation of the cluster, the chemical reaction between the sample surface atoms destabilized by the collision of the cluster and the reactive gas Can easily be provided, and an etching method and an apparatus having a sufficiently large etching rate comparable to those of a conventional ion beam etching apparatus can be provided.

(Example) Next, an example of the present invention will be described with reference to the drawings. First
The figure is a schematic diagram of the device. Here, a case is described in which silicon is etched using argon as a cluster constituent material and chlorine as a reactive gas. First, the argon cluster is generated as follows. A required amount of raw material argon gas is sent from a raw material gas cylinder 1 for cluster generation into a source chamber 2 having a vacuum exhaust mechanism, and is jetted therefrom through a nozzle 3 for cluster generation into an etching chamber 4 having a vacuum exhaust mechanism at a supersonic speed. Let it. As a result, a neutral cluster 5 in which a large number of argon are collected is generated. At this time, the flow rate of the argon gas is adjusted so that the pressure in the source chamber 2 becomes about 5 torr. The diameter of the cluster generating nozzle 3 is 0.5 mm,
The pressure in the etching chamber 4 during cluster generation is 2 × 10 ⁻⁴ torr.

Next, the obtained neutral cluster 5 is ionized by the impact of electrons emitted from the filament 6. The ionization cluster 7 is accelerated by a potential difference between the accelerating electrode 8 and the substrate 9, is converted into a parallel beam by a collimator 19, and collides with a silicon sample 10 mounted on the substrate 9. The acceleration voltage in this case is about 1 kV. Cluster ionization has the effect of selectively increasing the number of stable clusters, and thus contributes to stabilization of the etching rate.

In the etching, sputtering and surface atom destabilization occur in the silicon sample 10 due to the collision of clusters, and a chlorine gas 22 is supplied to the silicon sample 10 from a reactive gas introduction feeling 20 to each other, and the sputtering material of the silicon sample 10 is sputtered. And reacts with surface unstable atoms, and the reaction product proceeds by volatilizing as a gas from the substrate surface. At this time, the temperature of the base 9 is about 60 ° C., and the reactive gas flow rate is
10 sccm. The etching rate naturally depends greatly on the etching conditions, but a typical etching rate was 200 ° / min in this example. In the conventional method of etching with an argon ion beam, a typical etching rate is about
250Å / min. Furthermore, according to observation with a high-resolution transmission electron microscope near the surface of the silicon sample 10 on which the conventional argon ion beam etching was performed, many defects such as transitions and voids were found near the sample surface after the etching. On the other hand, in the case of the silicon sample in this example, almost no defects were observed, and it was found that the disorder of the crystal lattice on the etched surface was much smaller when the etching method of the present invention was used. Further, in the observation of the same silicon sample with a scanning electron microscope and a scanning tunneling microscope, in the case of etching with a conventional argon ion beam, irregularities of about 3% of the total etching amount were observed on the etched surface. In the example, the unevenness was about 1% of the total etching use. This means
This shows that an etching rate substantially equal to that of the conventional method was obtained with less damage to the substrate surface.

Note that, in the above-described embodiment, as a method of generating clusters, a method of generating gas by adiabatic condensation accompanying ejection into a high vacuum through a nozzle was used. The solid surface of the produced gas may be impacted by an ion beam, an electron beam, a laser beam, or the like, and the cluster may be desorbed to generate the gas. Also, etching can be performed by simultaneously using a cluster composed of highly reactive chemical species and a cluster composed of inert species. Further, as a method of ionizing clusters, a method using electron impact from a filament has been described, but a method of irradiating a laser beam or the like may be used. Furthermore, here, the method of accelerating the ionization and equilibrium beam of the cluster has been described. However, if the shape to be etched does not require anisotropy, the etching can be performed by using only the kinetic energy for cluster generation without ionization. proceed.

(Effect of the Invention) As described above, in the etching method of the present invention,
Since the low energy property of the cluster ion beam is used such that the energy of the constituent atoms or ions is about 1/100 of that of a normal ion beam, a large number of atoms Alternatively, since a substantial ion current can be sufficiently secured by using a cluster composed of ions, sputtering on the sample surface can be sufficiently caused.When a cluster composed of a highly reactive substance is used at the same time In this method, an assisting effect due to a chemical reaction between the generated highly reactive radicals and the sputtered atoms or molecules can be imparted to the etching, and the etching can be performed as fast as a conventional ion beam etching apparatus. Further, by flowing a highly reactive gas at the same time as the cluster irradiation, an assist effect due to a chemical reaction between the reactive gas and the sputtered atoms or molecules can be given to the etching, and the same effect as in a conventional ion beam etching apparatus can be obtained. Fast etching is realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an etching apparatus for explaining an embodiment of the etching method of the present invention. FIG. 2 is a sectional view of an ion beam etching apparatus for explaining the prior art. In the figure, 1: cluster gas cylinder, 2: source chamber, 3: nozzle, 4: etching chamber,
5: neutral cluster, 6: filament, 7: ionization cluster, 8: acceleration electrode, 9: substrate, 10: sample, 11: argon gas, 12: argon ion, 13: ion source, 14: cathode, 15: electron , 16: magnet, 19: collimator, 20: reactive gas inlet tube, 22: chlorine gas.

Claims (2)

(57) [Claims] 1. An etching step of supplying a chemical species to a sample surface and contacting the sample surface by desorbing the sample surface atoms from the sample surface by physical and / or chemical action of the chemical species on the sample surface. 3. The etching method according to claim 1, wherein chemical species having high reactivity are simultaneously supplied to the sample surface while supplying the chemical species as clusters to the sample surface. 2. A cluster generating part, an etching chamber part including a vacuum evacuation mechanism for introducing a cluster generated by the cluster generating part, a part for ionizing the cluster, and a sample held in the ionized cluster beam. A substrate, an accelerating electrode for accelerating the ionized cluster by an electric field toward the substrate, a collimator portion for converting the ionized cluster into a parallel beam, a portion filled with a gas reactive with the sample, and the reactive gas. And a portion for introducing a required amount of sample into the sample surface on the substrate in the etching chamber.