JPH0712033B2 - Fine pattern formation method by ion beam - Google Patents

Description

The present invention relates to a method for forming a desired pattern on a substrate by changing a substance by a synergistic effect of excited reactive particles and an ion beam.

Here, the excited reactive particles are, as described later, excited by microwaves at a position apart from the reaction chamber, and are composed of long-lived radicals that can be transported to the reaction chamber or short-lived reactive particles. It is a general term including reactively excited particles excited by a photochemically excited reaction in a broad sense including a wavelength electromagnetic light wave.

In the conventionally reported plasma etching, a pattern is formed by forming a resist pattern in advance and using it as a protective mask, and then performing a plasma reaction over the entire surface.

In addition, plasma oxidation for growing an oxide film on the surface of a semiconductor or a metal in a reduced-pressure oxygen discharge (oxygen plasma) can be formed at a low temperature, and thus has a wide range of potential applications.

In these processes, selective patterning was not possible without masking masking materials. Photochemical reactions have the effect of exciting gaseous molecules into reactively excited particles, but on the other hand, they have the characteristic that they can directly form a pattern by sending a reactive gas or reactively excited particles while irradiating a light pattern. There is. However, in many cases, it is inferior in fine workability as compared with pattern formation by an ion beam.

On the other hand, for pattern formation by an ion beam, experimental data has been issued by using several ion sources in ion beam lithography. Most of them use a liquid metal ion source, and there are reports such as Ga and Au.

Ion species such as B, As, Si and Be, which are important for maskless ion implantation, are extracted from a liquid metal ion source using a eutectic alloy. For this reason, it is necessary to add a mass separation function to the focused ion beam device, and an E × B mass separator or the like is often used. H using a gas ion source
There are some examples, but it is still technically difficult. Therefore, the pattern formation by the ion beam is not high enough to efficiently perform the direct pattern formation process due to the limitation of the ion source and the problem of the ion current.

On the other hand, the reactive excitation particles in the plasma or the reactive excitation particles due to the photochemical reaction can be directly treated with various substances such as etching and oxidation.

In view of the above situation, the present invention does not preliminarily install a resist pattern or a shielding pattern such as a SiO ₂ film on the substrate, imparts pattern information to the ion beam itself, and the ion beam and the reactive excitation particles on the substrate Changes in substances due to the action with the atmosphere occur only in selected locations, and in areas where there is no irradiation of the ion beam, such changes occur only infrequently, or hardly under appropriately selected conditions. The main purpose is to do so, and the direct pattern formation can be efficiently performed in a wider range while maintaining the miniaturization of the pattern by the ion beam.

To outline the method of the present invention, an ion optics system is provided on a substrate in an atmosphere containing reactively excited particles made possible by differential evacuation, etc., by using an ion beam having an appropriately selected acceleration energy. Selective treatment of reactively excited particles that draws a two-dimensional pattern by forming an image and makes a reaction on the substrate by the synergistic effect of the reactively excited particles and the ion beam in the same elementary process. Can be summarized as a possible pattern formation method. Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 shows that in the substrate portion in the reaction chamber, pattern information is given to the ion beam of the present invention, and the ion beam is projected on the substrate in the atmosphere containing the reactive excitation particles through the ion optical system. It is a schematic block diagram of the apparatus which can form in the state which patterned the change of the substance which arises when an ion beam and the atmosphere of a reactive excitation particle act on a substrate substance. In FIG. 1, which is one example of the configuration, an ion beam 1 to which pattern information is added is an ion beam 1 focused by an ion optical system from an upper casing through a diaphragm 2 to form a substrate. Reach 3. There may be various types of ion beam focusing control and deflection systems above the aperture stop 2, but it is not the main purpose of the present invention to specify these in detail. These are related to ion-beam lithography, which is currently making remarkable progress.

Several systems of focused ion beam control and deflection have been reported. Speaking from the side closer to the substrate, as shown in FIG. 1, first, there is a deflection electrode 23 for XY deflection.
In front of the deflection electrode 23, there is an objective lens 24 composed of an Einzel lens or the like. The previous stages before this differ depending on the type of ion source and whether it has a mass separation function. Therefore, details of the ion beam control and deflection system will not be shown in FIG.

Field emission liquid metal ion source consisting of a single element (Ga, etc.)
In case of, the mass separation function is not required. In this case, the order of the ion source, the extraction electrode, the movable diaphragm, the converging lens, the deflector, the substrate, and the like is one configuration example.

On the other hand, in the case of a liquid metal ion source using a eutectic alloy (Si-Au, B-Ni-Pt, etc.), an ion source, an extraction electrode, a condenser lens, mass separation (E × B method), a deflector, a diaphragm ,
One example of the configuration is the order of the objective lens, the main deflector, and the substrate.

In addition, with an idea similar to the electron beam drawing device, for example,
It is also possible to perform drawing by the variable shaped beam system using the first diaphragm and the second diaphragm having a square opening.

As with the electron beam transfer technology, reduction transfer is possible with ion beams.

Using gas ion sources such as H, He, Ne, Ar
It is possible to transfer ions with KeV energy with a reduced ion optical system of about 10: 1. In the case of ion beam transfer, the mask is one problem, but it is also reported that a self-supporting mask made of a metal film or the like can achieve 10: 1 reduction transfer with high accuracy. There is a difference between pattern formation using an ion beam and pattern formation using an electron beam or light. The patterning of electron beam and light may be considered as local irradiation of energy beam, and eventually it does not remain in the substrate. On the other hand, the local irradiation and implantation of the ion beam have two different properties: the surface of irradiation of the energy beam and the local implantation and irradiation of the material beam. In the above sense, the ion beam implantation has a large difference from the light and electron beams in that there may be a process when the implanted material remains in the substrate.

Since the ion beam has the aspects of local transport, implantation, and deposition of the material beam, there is a big difference between the single-stroke writing beam writing and the ion beam batch transfer as a direct pattern forming process.

Even if there is a problem of making an ion beam transfer mask,
Being able to inject or introduce a fine material beam into a plurality of locations at the same time is an important concept in manufacturing an integrated circuit or the like having a complicated pattern structure by a direct pattern formation method.

In particular, in addition to the process of implanting impurities such as B and Si,
If O or N can be injected, it will bring an epoch-making method as an isolation method such as IC or a method for locally modifying the material layer.

The possible methods of pattern formation by the ion beam have been described above.

Next, the structure of the reaction chamber will be described. Since the required vacuum degree differs greatly between the reaction chamber in which the substrate is installed and the ion focusing optical system, differential evacuation is performed by multiple evacuation systems, and the reactive excitation particles to the ion optical system are used. Prevent pollution.

Further, the degree of vacuum required for focusing and deflection control of the ion beam will be maintained.

The focused ion beam 1 is applied to the substrate 3 to draw a pattern. The substrate 3 is installed on the substrate support 4, and the support is configured so that the temperature of the substrate portion such as low temperature heating can be controlled if necessary.

The support base 4 is installed on the X-Y moving mechanisms 5 and 6, and can perform precision positioning and precision movement equivalent to those of an ordinary ion beam drawing apparatus. Various materials in the reaction chamber 7 are composed of materials that are not corroded by reactive excitation particles such as plasma.

In the embodiment shown in FIG. 1, the casing of the ion beam optical system is an exhaust port.
Can be exhausted as needed from multiple exhaust ports such as 8a. The reaction chamber 7 is exhausted through the exhaust port 9. The pressure in the reaction chamber is determined by the exhaust capacity of these exhaust ports 9 and 8a.

On the other hand, electric field-excited plasma, which is one of the important elements among the reactive excitation particles, can be introduced through the transport tube 10. 2.45 GHz microwave generated by magnetron oscillation is introduced into the waveguide 11a in front of the transport tube,
A quartz tube reaction part 12 is inserted in a part of the waveguide. Impedance matching is maintained at the end of the waveguide by a matching device 11b. CF ₄ + O ₂ gas is introduced into the quartz tube through the introduction tube 12a at about 0.1 Torr. When introduced at a pressure of this level, the generated plasma hardly spreads even with an increase in electric power, becomes in a stable state, and the matching condition is not broken even with a change in gas flow rate. If the plasma transport tube 10 is coated with Teflon, the active species generated in the discharge part can be introduced into the reaction chamber 7 without being significantly attenuated even in the reaction chamber about 1 m away. That is, such active species are long-lived radicals.

The 2.45 GHz microwave-excited plasma etching method has been reported so far. According to this method, various thin films such as polycrystalline silicon, Si ₃ N ₄ , SiO ₂ , Nb, W, Mo and photoresist are etched. The condition is CF
Etching is possible when the pressure of ₄ is about 0.12 Torr and Pr = Po ₂ / P _CF 4 is about 0 to 4. The advantage of the plasma etching method based on this excitation method is that no electrode for discharge is required in the reaction chamber 7. In the above plasma excitation method,
Depending on the conditions, plasma oxidation or nitridation with plasma-activated oxygen or nitrogen using O ₂ or N ₂ as the introduction gas is also possible.

In the above description, the reactive excitation particles in the reaction chamber 7 can reach the reaction chamber without being significantly attenuated even if they are generated at a distance of about 1 m, as described above. It is a long-lived radical. But,
The means for forming the reactive excitation particles in the reaction chamber 7 is not limited to plasma excitation. Recently, there have been many reports of reactive gas particles caused by photoexcitation reactions such as infrared light, visible light, ultraviolet light and deep UV light (short wavelength ultraviolet light). Further, in some cases, the gas phase particles can be excited by the electromagnetic light wave chemical reaction even by the electromagnetic light waves of a short wavelength from the deep UV light to the X-rays. As the photochemical reaction process, for example, Si
It is known that dry etching can be performed by optically exciting Cl ₂ or Br ₂ gas with a laser beam of 4880Å or 2570Å. GaAs and InP can also be etched by the reaction of CH ₃ Br gas with deep UV excitation light. The pattern formation method by ion beam drawing having pattern information, which incorporates the effect of the reactive gas particles by the electromagnetic light wave photochemical reaction proposed as one embodiment of the present invention, is based on the findings of the reports of various reactions described above. There is.

In FIG. 1, a light beam 13 is a scannable light beam for exciting a photochemical reaction. The light flux 13L from the light source is used as a light source for exciting a photochemical reaction from a laser or the like. A light flux control system 14 is arranged for temporally switching the light flux 13L or for spatially changing the direction, position, etc. of the light flux. The light flux 13M emitted from the light flux control system 14 becomes a light flux 13a which reaches the vicinity of the sample through the reflecting mirror 15, the reflecting mirror 16, the light flux transmitting window 17, and the flat or concave cylindrical reflecting mirror 18.

The gas for photochemical reaction is introduced into the reaction chamber 7 from the gas sources 20 and 21 through the valve 19.

The photochemical reaction gas is subjected to photochemical excitation in the light passage space in the reaction chamber such as the position of the light flux 13b in the depressurized atmosphere.

Further, the luminous flux 13a directly irradiated to the vicinity of the sample surface or the sample surface acts more strongly on the photochemical reaction. In particular, when the sample surface is directly irradiated, local heating due to photoexcitation of the sample surface, electron-hole excitation, and the like are added, so that a multi-element reaction mechanism is added.

It is also possible to make the light beam 13 scannable to improve the uniformity and controllability of light irradiation on the sample surface. Mechanically mirrors 15, 1
6 and 18 may be driven by a fine movement control mechanism. Faster operation is possible by installing an electronic optical switch or optical path changing device in the light flux control system 14.

In addition, optical switch and half mirror with some polarization,
If you use microlens array, optical fiber, etc.,
Multiple light fluxes can be processed simultaneously and in parallel. As a result, it becomes possible for each of the plurality of light beams to have their own temporal discontinuity and spatial arrangement.

The optical system including the light flux controlling system 14 and the mirrors 15, 16 and 18 shown in FIG. 1 is one embodiment. It will be understood that various other light flux group controls are possible.

It is also possible to separately provide a plurality of light beam transmitting windows in the ion beam pattern drawing system as shown in FIG. 1 and to make a plurality of light beam groups enter the respective light beam transmitting windows spatially and temporally intermittently. Alternatively, there is an advantage in that there is no difference in the control of the light flux between the vacuum and the atmosphere. Therefore, it is also possible to bring the above-mentioned various luminous flux group control systems into the reaction chamber 7.

It is possible to irradiate a plurality of light fluxes with a spatial distribution and a temporal discontinuity in a specific case within the substrate by making the above light flux groups enter obliquely in the vicinity of the substrate in the reaction chamber.
When installing the light flux control system in the reaction chamber, a quartz plate, so that the light flux control system is not damaged by the reactive excitation particles,
It is necessary to provide a storage container that can protect the material of Teflon coat.

As described in detail above, by utilizing the fine pattern forming method by the ion beam of the present invention, plasma treatment by microwave-excited long-lived radicals, photochemical treatment by photochemically reactive excited particles, and excitation of these two kinds A fine pattern drawing function by an ion beam can be added to a process or the like in which reactively excited particles excited by the method are used together.

Further, according to the present invention, the portion hit by the ion beam is more affected than other portions by the reaction effect of the ion beam and the reactive excitation particles on the substrate, for example, local damage by various particles on the substrate, ion implantation effect, etc. Is also deeply etched. The parameters that change the reaction strength such as plasma long-lived radical formation conditions and photochemically excited reaction conditions are set so that almost no reaction occurs on the substrate when the ion beam is not applied, and when the ion beam is irradiated. It can be adjusted so that the reaction is promoted and the etching occurs only there. That is, by finding such a condition, resistless pattern formation etching can be performed. In some cases, the textured surface of the etched wafer can be further patterned by maskless ion implantation after blocking the reactive gas by the ion beam.

Further, regarding the oxidation process using reactively excited particles such as plasma oxidation, it is effective for controlling the depth of the oxide layer and patterning, and for improving the film quality by ion implantation of an element other than oxygen after oxidation and the patterning thereof. is there.

The ion beam writing system shown in FIG. 1 shows a part of the ion beam control system of the scanning system, but it is obvious that this can be applied to other known ion beam writing systems.

According to the present invention, a sub-micron pattern can be formed on a substrate wafer by a resistless direct process in a vacuum exhaust system without exposing it to the atmosphere.

The present invention can be used as part of a direct pattern formation process which is expected to progress in the future.

This can contribute to improving the efficiency and performance of manufacturing various electronic devices, integrated circuits and the like.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a direct pattern forming method using an ion beam having pattern information in an atmosphere containing reactively excited particles according to the present invention. In the figure, 1 is an ion beam having pattern information, 2 is a diaphragm, 3 is a substrate, 4 is a substrate support, 5 and 6 are X and Y moving stages, 7 is a reaction chamber, 8a is an exhaust port, and 9 is an exhaust. Mouth, 10 is a plasma transport tube, 11a is a microwave waveguide, 12 is a quartz tube reaction section, 12a is a gas introduction tube, 13 is a light beam for photochemical reaction, 14 is a light beam control system, 15, 16 and 18 are reflection mirrors, 17 is a transparent window, 20,
Reference numeral 21 is a gas source, 19 is a gas introduction tube, 22 is a part of an ion beam optical system, 23 is a deflector, and 24 is an objective lens.

Claims (3)

[Claims] 1. An ion beam focusing optical system is arranged in a reaction chamber so that differential pumping is possible; the reaction chamber is housed in the reaction chamber in an atmosphere containing reactive excited particles. The substrate is irradiated with an ion beam to which predetermined pattern information is given from the ion beam focusing optical system; a predetermined amount of light is applied to the substrate due to a change in substance due to a synergistic effect of the ion beam and the reactive excitation particles. Forming a pattern of the above; and a fine pattern forming method using an ion beam. 2. The reactive excited particles are composed of long-lived radicals generated at a distance from the reaction chamber and transported to the reaction chamber. The method for forming a fine pattern according to item. 3. The reactive excitation particles are those excited by an electromagnetic light wave chemical reaction by a light beam introduced into the reaction chamber from outside the reaction chamber through a transmission window. The fine pattern forming method according to claim 1.