JP2000114207A - Microfabrication method and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microfabrication method capable of using FAB, of increasing a high selection ratio for etching between a sample to be processed and a mask material, and of processing a fine pattern satisfactorily at a high aspect ratio. SOLUTION: The microfabrication method is designed to transfer a processing pattern made of a mask material, and comprises steps of mounting a sample 16 to be processed on a cooling stage 15 that is provided within a vacuum container 11 together with an FAB source 13, forming a processing pattern on the surface of the sample 16 using a mask material 17 such as a resist material, and having the surface of the sample 16 irradiated by a FAB source 14 emitted from the source 13. In this case, by cooling the material 17 by the stage 15, the ratio of the processing amount of the sample 16 to that of the material 17 is increased, and thus the sample 16 is processed at a higher aspect ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submicron level fine processing method for semiconductors and optical parts, and more
The present invention relates to a fine processing method capable of performing an etching process with a high aspect ratio using (high-speed atomic beam).

[0002]

2. Description of the Related Art In semiconductor devices and optical components,
In some cases, fine processing with a size of submicron or less, particularly 0.1 μm or less is required. A possible processing method for such an ultra-fine etching process is a conventional anisotropic etching using plasma. In this method, a fine pattern of a resist film is formed on the surface of a sample to be processed in advance, and etching is performed by using this as a mask and using plasma. In other words, in the anisotropic etching, a gas having an etching property is ionized to be in a plasma state, and an ion generated by the ionization is given an electric field so as to have directionality, and the ions are irradiated on a sample to be processed. In this way, an etching process is performed.

However, in processing using plasma, it is difficult to perform processing with a high aspect ratio because the directionality of energetic particles is poor. In addition, etching of a fine pattern using an ion beam can be considered, but usually,
Since an insulating material such as a resin is often used as a mask material for forming a fine pattern, the charge is significantly affected by the charge. Since the ion beam itself has an electric charge, it is difficult to perform anisotropic processing, that is, to realize a vertical processing wall under the influence of the surface charge-up.

In order to avoid such a problem, FAB
A microfabrication method using is studied. In particular, FAB
Since is a high-speed atomic or molecular beam that is electrically neutral and excellent in straightness, it has excellent characteristics for processing with a high aspect ratio. In the FAB, ions in the plasma are accelerated by an electric field, exchange charges with residual gas particles in the beam emission holes, and are neutralized and emitted. When usually used for processing such as etching,
About 100 eV to 10 keV are used.

[0005]

SUMMARY OF THE INVENTION However, FAB
However, there is a problem that, for example, a resist film serving as a pattern mask is also etched. In particular, when the minimum dimension of the fine processing pattern is 0.1 μm or less, the resist film thickness becomes thin, and it becomes difficult to perform processing with a high aspect ratio. In this case, it is necessary to increase the thickness of the resist film itself as a mask material for the fine pattern, but it is necessary to make the resist film as thin as possible in order to form an ultra-fine pattern. It is necessary to increase the etching selectivity between the sample to be processed and the mask material. However, since FAB has strong energy, it is difficult to obtain a high selectivity by a conventional processing method using general FAB.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to obtain a high etching selectivity between a sample to be processed and a mask material by using a FAB. It is an object to provide a fine processing method capable of performing processing.

[0007]

According to a first aspect of the present invention, an FAB source and a cooling stage are provided in a vacuum vessel, and a sample to be processed is mounted on the cooling stage, and a surface of the sample to be processed is provided. Has a processing pattern formed by a mask material such as a resist material, and F is discharged from the FAB source.
A fine processing method for transferring a processing pattern of the mask material by irradiating AB to the surface of the sample to be processed, wherein the mask material is cooled by the cooling stage, and the processing amount of the mask material is reduced. A micromachining method characterized by increasing the ratio of the processing amount of a sample to be processed and performing processing with a high aspect ratio on the sample to be processed.

According to the present invention, the mask material such as the resist is cooled by the cooling stage, thereby improving the etching resistance by the FAB. Therefore, the etching rate of the mask material can be significantly reduced with respect to the etching rate of the material to be processed. Thus, even when the mask material is thin for forming a fine pattern, etching with a high aspect ratio can be performed on the material to be processed.

As a medium for cooling the cooling stage,
Alcohol or CFC-based refrigerants may be used. Thus, the cooling stage can be cooled to −60 ° C. by using the alcohol-based refrigerant, and the cooling stage can be cooled to about −70 ° C. by using the CFC-based refrigerant.

Further, liquefied nitrogen may be used as a medium for cooling the cooling stage. Thereby, it is possible to cool to about 77K (-195 ° C) by using liquefied nitrogen.

Further, liquefied hydrogen or liquefied helium may be used as a medium for cooling the cooling stage. This makes it possible to cool the cooling stage to about 4K (−269 ° C.) by using liquefied hydrogen or liquefied helium.

The invention according to a second aspect is characterized in that the cooling stage is cooled by a cooling medium, and the cooling medium is brought into contact with a sample to be processed. This allows the cooling medium to come into direct contact with the sample to be processed, as compared to placing the sample on the plate of the cooling stage, thereby improving the cooling efficiency of the sample to be processed.

Further, a thermoelectric element may be provided on the cooling stage, and the mask material may be cooled by removing heat of the sample to be processed by the thermoelectric element.
Thus, the sample to be processed can be cooled by a thermoelectric element such as a Peltier element, and can be easily cooled without using a refrigerant such as liquefied nitrogen. That is, when a thermoelectric element is used, the cooling mechanism becomes compact and electrical control is easily performed, so that a simple and effective cooling method can be realized.

According to a third aspect of the present invention, the pattern of the mask material formed on the surface of the sample to be processed has a three-dimensional shape, is processed by the FAB, and the three-dimensional shape is transferred to the sample to be processed. It is characterized by being performed. Thereby, it is possible to perform fine processing of the three-dimensional shape of the sample to be processed.

The pattern of the mask material formed on the surface of the sample to be processed may have a two-dimensional shape, and may be processed by the FAB so that the three-dimensional shape is transferred to the sample to be processed. Thereby, it is possible to perform fine processing of the three-dimensional shape of the sample to be processed.

Preferably, the minimum dimension of the mask material pattern is 0.1 μm or less. This makes it possible to perform etching of a fine pattern, which is difficult with conventional etching using plasma or etching using ion beams.

According to a fourth aspect of the present invention, there is provided a vacuum vessel, a FAB source disposed in the vessel, and a stage on which a sample to be processed is mounted. It is characterized in that the sample is cooled to such an extent that the mask material arranged on the sample to be processed increases the etching resistance against FAB.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding parts will be denoted by the same reference characters.

FIG. 1 shows a fine processing apparatus according to an embodiment of the present invention. The vacuum vessel 11 is provided with a pump 12 so that the inside of the vacuum vessel can be evacuated. In the vacuum container 11, FAB
A source 13 is provided so that FAB of various energies can be irradiated. Further, a cooling stage 15 is provided, and a sample 16 to be processed is mounted on the cooling stage.
Etching can be performed by irradiation with B. Reference numeral 17 denotes a mask material such as a resist.
The sample 16 to be processed is etched according to the pattern 7. This apparatus includes a refrigerant source 20, and a refrigerant such as a CFC-based refrigerant or liquid nitrogen cools a cooling stage. Fluorinert (trade name), which is a Freon-based refrigerant, can be cooled to about -70 ° C, and liquid nitrogen can be cooled to about -195 ° C. In addition, when alcohol is used as the refrigerant, it can be cooled to -50 ° C, and when liquid helium or the like is used, it can be cooled to an extremely low temperature of about -269 ° C.

The cooling stage 15 has a refrigerant inflow path 18 and a refrigerant outflow path 19, and the above-mentioned refrigerant circulates through the cooling stage 15 to cool the cooling plate on which the sample to be processed of the cooling stage 15 is mounted. Then, the sample 16 to be processed and the mask material 1 for the resist film provided on this surface
Cool 7 The cooling stage 15 is rotatable with a driving mechanism 21. Further, an infrared radiation thermometer 23 is provided in the vacuum vessel 11 so that the surface temperature of the cooling stage 15 can be detected. Also, the controller 24
The temperature of the cooling stage 15 may be controlled to a required temperature by controlling the coolant source 20 via the cooling medium.

Here, as the FAB, SF ₆ , CH
A beam formed from a gas such as F ₃ , Cl ₂ , Ar, and O ₂ is used. Samples to be processed include Si, Ga, A
Substrates such as s and glass are used. Note that a parallel plate type beam source is preferable as the FAB source. This is a plate-shaped cathode having a large number of atom emission holes, and a plate-shaped anode having a large number of similarly placed holes placed opposite to the plate-shaped cathode, are arranged facing each other. A positive potential is applied to the anode. A gas is introduced between the cathode and the anode, the gas is turned into a plasma state, and the generated ions are accelerated to neutralize the atoms when passing through the atom emission holes of the plate-shaped cathode. To form According to such an apparatus configuration, it is possible to form an FAB that is uniform, has high straightness, and has a relatively large beam diameter.

FIG. 2 shows a modification of the cooling stage 15 shown in FIG. The stage 15 has an opening 15B in a cooling plate 15A on which a workpiece 16 is placed. The workpiece 16 is fixed to the cooling plate 15A while being sealed via the clamp 26 and the O-ring 27. Accordingly, the refrigerant that has entered the stage 15 from the inflow path 18 directly contacts the workpiece 16 through the opening 15B. Then, the refrigerant is discharged from the stage 15 through the outflow path 19. As a result, the coolant directly contacts the sample 16 to be processed, so that the efficiency of cooling the sample to be processed can be increased. When the sample to be processed is cooled using the cooling stage, the temperature of the sample is suppressed from rising during the FAB irradiation, and the temperature of the pattern material on the surface to be processed is suppressed.
The chemical reactivity and the chemical sputtering amount of the pattern material are reduced, and as a result, the selectivity (the processing amount of the resist film / the processing amount of the sample to be processed) can be increased.

FIG. 3 shows still another modification of the cooling stage 15. In the case of this embodiment, a thermoelectric element 29 such as a Peltier element is mounted on the cooling stage 15. The thermoelectric element 29 transfers the heat of the front surface to the rear surface side by supplying a current. Then, water is supplied from the inflow path 18 of the refrigerant in the cooling stage 15 and discharged to the outflow path 19, thereby removing the heat transferred to the back side of the thermoelectric element 29.
That is, heat is absorbed by the thermoelectric element 29 from the back surface side of the sample to be processed 18, and is cooled by the cooling stage 15, so that the sample to be processed 16 can be cooled. The cooling temperature depends on the number of thermoelectric elements, the capacity, and the like, but cooling of about several tens of degrees Celsius is possible. According to such a method for cooling a sample to be processed, the sample to be processed can be cooled by a combination of a commercially available Peltier element and a general water cooling mechanism. Simpler and more efficient cooling is possible as compared with.

4 to 8 show an embodiment of the fine processing method of the present invention. FIG. 4 shows a case where the cooling plate 15A of the cooling stage is cooled to about -70 ° C. using a chlorofluorocarbon-based refrigerant. In this embodiment, the sample to be processed 16 is Ga
It is a thin plate of As, Si, polyimide or the like. As a result, an electron beam resist such as PMMA is arranged as the mask material 17, and an uneven pattern having a width of 50 nm and a pitch of 100 nm is formed. When the workpiece 16 is cooled in this way, the mask material 17 is also cooled, and the mask material 17 has high etching resistance to FAB.
For this reason, when the FAB 14 is irradiated, a portion of the sample 16 to be processed that is not covered with the mask material 17 is etched,
The hatched portions in the figure are removed. At this time, the hatched portion of the mask material 17 is also etched by the FAB irradiation, but the mask material is cooled and has high etching resistance as described above. For this reason,
Removals by irradiation of FAB is slight, on the order _{L 1.} On the other hand, in the material 16 to be processed, the etching rate for FAB is not related to cooling. Therefore the typical etching rate obtained for FAB, etched to a depth L ₂ by irradiation of the same time FAB progresses. Thus, by cooling the sample to be processed, the FA of the mask material is reduced.
The etching resistance to B can be increased, and the etching rate of the mask material can be extremely reduced with respect to the etching rate of the sample to be processed. Therefore, an etching groove having a high aspect ratio as shown in the drawing can be formed in the sample 16 to be processed.

Next, an example of an experimental result according to the above embodiment will be described. Using the above-mentioned parallel plate type FAB source, CHF ₃ gas, a gas flow rate of 20 sccm, a discharge voltage of 3 kv, a discharge current of 50 mA, and a beam diameter of 80 mmφ.
Generate AB. A quartz glass substrate provided with a photoresist pattern having a thickness of about 6000 ° is arranged at a distance of 200 mm from the beam source. This substrate has a thickness of 0.5 mm and a size of 20 × 20 mm. Then, the processing chamber pressure is maintained at about 2 × 10 ⁻⁴ Torr, and the stage is set at 2 rpm.
Rotate gently to the extent. This stage can be cooled using alcohol as a refrigerant, and (A) normal temperature (25 ° C.)
) And (B) etching at a low temperature of about −15 ° C. The experimental results are as follows: (A) At room temperature (about 25 ° C.), resist processing amount 250Å substrate processing amount 1294Å selectivity 5.2 (B) At -15 ° C., resist processing amount 16Å substrate processing amount 1142Å selectivity A result of 71.4 was obtained. Therefore, it was demonstrated that cooling the substrate to about −15 ° C. improves the selectivity from 5.2 to 71.4, about 14 times.

FIG. 5 shows a fine processing method according to the second embodiment. In this case, the cooling stage 15 is cooled to 77 K (−195 ° C.) using liquid nitrogen. The sample 16 to be processed includes quartz glass, glass, GaAs, Si,
Polyimide and the like. A photoresist is used as the mask material 17. The mask material 17 is a pattern having a three-dimensional shape like a sawtooth wave as shown in the figure. When this is irradiated with the FAB 14, the mask material 1
Portions not covered by 7 or thin portions are etched by FAB. Then, the etching of the mask material 17 progresses along with the etching of the sample 16 to be processed, and when the FAB 14 is irradiated until the mask material 17 finally disappears,
Portions indicated by oblique lines in the figure are removed by etching. Therefore, the sawtooth wave shape as shown in FIG.
6 is formed. At this time, since the mask material 17 is cooled to a low temperature by the liquid nitrogen, the etching resistance of the mask material to FAB is enhanced, and the etching rate of the material to be processed can be significantly increased with respect to the etching rate of the mask material. . Thereby, even if the three-dimensional shape of the mask material has a low aspect ratio, the aspect ratio of the workpiece to which the mask material has been transferred can be significantly increased.

In the quartz glass processing example, the FAB uses the above-mentioned parallel plate type beam source, uses CHF ₃ gas, has an acceleration voltage of 2 to ₃ V, a discharge current of 200 mA, and a beam diameter of 80 mmφ. The three-dimensional shape of the mask material is formed by using a stamp method or an electron dose control exposure method. In this way, the minimum pattern width is 0.1 to
A sawtooth wave structure of 1 μm and height of 1 to 5 μm can be realized. This makes it possible to manufacture a micrograting structure as shown in FIG. 6A and a microlens array as shown in FIG. 6B.

FIG. 7 shows an example in which a three-dimensional structure is formed on a sample to be processed from a two-dimensional resist film pattern. FIG.
(A) shows that a sample to be processed is 2
This shows that a two-dimensional resist pattern is formed.
That is, the two-dimensional Cr pattern 4 is formed on the glass mask 41.
1A, this pattern is transferred to a resist film 17 applied to the surface of the sample 16 to be processed by using a normal exposure method. This pattern is a groove having various widths formed in a direction perpendicular to the paper surface. Then, as shown in (b), the work sample 16 is cooled to, for example, about -70 ° C.
The irradiation of B14 is performed. Thereby, the etching resistance of the mask material 17 made of a resist film is increased by cooling, and the etching rate is significantly reduced. On the other hand, since the etching rate of the sample 16 to be processed made of, for example, quartz glass is not different from that at a normal temperature, a relatively high etching rate can be obtained. Then, by continuing the etching by the FAB 14 until the mask material 17 completely disappears, the etching speed of the portion not covered by the mask material 17 becomes significantly higher than the etching speed of the covered portion. For this reason, after the mask material 17 has disappeared, the etching rate of the portion where the mask material was present and the etching speed of the portion where the mask material was not present remain unchanged. Accordingly, the narrow portion of the resist pattern is filled, and the sample 16 to be processed is processed into a three-dimensional shape as shown by a dotted line in the figure. Thus, by forming a two-dimensional pattern on the mask material, a three-dimensional structure can be formed on the sample to be processed.

For example, in order to satisfy such FAB processing conditions, a vacuum vessel pressure with a processing pressure of 1 to 5 × 10 ⁻³ Torr is used. Also, the diameter of the FAB discharge hole is 3 to 5 mmφ.
By using a 5 mm long FAB source.

FIG. 8 shows an example of forming a three-dimensional structure on a sample to be processed from a two-dimensional glass mask pattern. A pattern 41A of a Cr film is formed on the glass mask 41,
Two-dimensional patterns with different gaps are created. Exposure is performed with a distance L between the glass mask 41 and the substrate 16 on which the resist 17 is applied. Distance L is 1-100μ
m is appropriate. When the thick resist 17 is used, the light spreads due to the effect of light diffraction and scattering, and a photosensitive characteristic as if there was a continuous light quantity change is obtained. By such a method, the resist 17 can be processed into a three-dimensional shape. Therefore, as described above, the three-dimensional pattern can be transferred to the substrate by the FAB process using the resist pattern as the mask material 17.

However, if the shape of the three-dimensional resist pattern is deformed during actual processing by FAB, the processed shape of the substrate differs from the design value. At this time, by cooling the resist 17 and minimizing the etching of the resist 17, it is possible to perform processing by FAB that accurately transfers the three-dimensional shape of the resist 17 to the substrate to be processed. For example, as shown in FIG.
Placed on a stage cooled to 0 to -70 ° C, CHF ₃
Alternatively, an FAB source using SF ₆ gas is set to an acceleration voltage of 3 kv,
When the resist 17 formed on the quartz glass substrate 16 is irradiated with a discharge current of 100 mA and a beam diameter of 80 mmφ, the three-dimensional shape of the resist 17 is accurately transferred to the substrate 16 as shown by a dotted line in the figure due to the above-described effect. You. That is, in the processing at room temperature (room temperature), the shape of the three-dimensional pattern of the resist 17 is deformed during the etching by the FAB, and it is difficult to perform the processing with high accuracy. This is FAB14
When the resist 17 is irradiated on the resist 17, the surface layer is heated and deformed by Joule heating. By using the cooling stage, this adverse effect can be prevented and high-precision processing can be performed.

[0032]

As described above, according to the present invention, F
By cooling the sample to be processed at the time of AB irradiation, the etching resistance of the mask material is increased, and a fine pattern with a high aspect ratio can be processed on the sample to be processed. That is, in the conventional FAB processing method, processing with a high aspect ratio depends on the selection ratio of the mask material. According to the present invention, since the selectivity of the pattern material can be dramatically improved, processing with a higher aspect ratio, particularly processing with a minimum pattern dimension of 0.1 μm or less, can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a microfabrication apparatus according to an embodiment of the present invention.

FIG. 2 is a view showing a modification of the cooling stage in FIG.

FIG. 3 is a view showing a modification of the cooling stage in FIG. 1;

FIG. 4 is a diagram showing one example of a fine processing method according to an embodiment of the present invention.

5A and 5B are diagrams for explaining transfer of a three-dimensional pattern, wherein FIG. 5A shows a stage of irradiating the FAB, and FIG.

FIG. 6A shows a micro-grating structure,
(B) shows a microlens array structure.

7A and 7B are explanatory diagrams of a method of forming a three-dimensional shape from a two-dimensional pattern of a resist, wherein FIG. 7A shows a step of forming a two-dimensional pattern of a mask material on a sample to be processed, and FIG.
4 shows a stage of forming a three-dimensional shape of a sample to be processed by AB irradiation.

8A and 8B are explanatory diagrams of a method of forming a three-dimensional shape from a two-dimensional pattern of a glass mask, wherein FIG. 8A shows a step of forming a three-dimensional pattern of a mask material on a sample to be processed, and FIG.
Indicates a stage of forming a three-dimensional shape of the sample to be processed by the FAB irradiation.

[Explanation of symbols]

 Reference Signs List 11 vacuum chamber 13 FAB source 14 FAB 15 cooling stage 16 sample to be processed 17 mask material 18 cooling medium inflow path 19 cooling medium outflow path 20 refrigerant source

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H096 AA25 AA28 EA08 EA30 FA03 HA11 5C001 AA08 BB02 CC08 5F004 AA05 BA11 BA20 BB25 BD03 CA05 DA04 DA16 DA18 DA23 DA26 DB00 DB01 DB19 DB20 DB25 DB27 EA08 EA30 EA37

Claims (4)

[Claims] 1. A vacuum vessel is provided with a FAB source and a cooling stage, and a sample to be processed is mounted on the cooling stage, and a processing pattern is formed on the surface of the sample by a mask material such as a resist material. A fine processing method of transferring a processing pattern of the mask material by irradiating the FAB emitted from the FAB source to the surface of the sample to be processed, wherein the mask material is cooled by the cooling stage. Thereby increasing the ratio of the processing amount of the sample to the processing amount to the processing amount of the mask material, and performing processing with a high aspect ratio on the sample to be processed. 2. The micromachining method according to claim 1, wherein the cooling stage is cooled by a cooling medium, and the cooling medium is brought into contact with a sample to be processed. 3. The pattern of a mask material formed on a surface of a sample to be processed has a three-dimensional shape, is processed by the FAB, and the three-dimensional shape is transferred to the sample to be processed. The microfabrication method according to claim 1. 4. A vacuum container and an FA disposed in the container.
A B source and a stage on which the sample to be processed is mounted, and the stage is provided with a cooling device so that the mask material placed on the sample to be processed is so large that the etching resistance against FAB increases. A fine processing device characterized by cooling.