JP3131594B2 - Reactive ion etching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive ion etching apparatus. More specifically, the invention of this application relates to a magnetic head used for writing to and reading from a magnetic disk, a microtransformer incorporated in a magnetic integrated circuit, a microinductor, a magnetic sensor, a spin-scattering magnetoresistance effect element, a spin valve element, Dry etching of magnetic materials useful for manufacturing a group of quantum effect magnetic devices such as ferromagnetic tunnel junction devices, spin field effect devices, spin diodes, and spin transistors, as well as components for micromachines such as thin film magnets and magnetostrictive actuators The present invention relates to a new reactive ion etching apparatus characterized as an apparatus or the like.

[0002]

2. Description of the Related Art In general, micro semiconductor elements such as VLSI and magnetic elements are manufactured by combining two processes of lithography and etching. The lithography technology is a technology for making fine patterns on a photosensitive film such as a resist film applied on the surface of a material to be processed (a thin film of a semiconductor or a thin film of a magnetic material). There is an electron beam lithography technique for exposing using a beam, and an ion beam lithography technique for exposing using an ion beam.

[0003] The etching technique is a technique for transferring a resist pattern formed by lithography to a semiconductor thin film or a magnetic thin film as a material to be processed to manufacture an element. Etching techniques include wet etching, argon ion milling, and reactive ion etching. Among these etching methods, the reactive ion etching method can transfer a pattern produced by lithography most accurately, is most suitable for fine processing, has a fast etching speed, and is the most excellent method. is there. Actually, large-scale integrated circuits and semiconductor memories of semiconductors are manufactured by this method.

[0004] In the reactive ion etching method, a workpiece is placed in a plasma of a reactive gas and an electric field is applied.
By the ion which is perpendicularly incident on the surface of the workpiece,
This is a method in which atoms on the surface of a workpiece are chemically and physically stripped sequentially, and anisotropic processing in which a portion not covered with a mask is cut vertically along the boundary of the mask is possible. Therefore, it is a method capable of transferring a fine and sharp shape. In the reactive ion etching method, chemically active species such as reactive gas ions and radicals generated in the plasma are adsorbed on the surface of the workpiece and chemically react with the workpiece, resulting in a surface with low binding energy. A reaction layer is first formed. Since the surface of the workpiece is exposed to the vertical impact of positive ions accelerated by the electric field in the plasma, the loosely bonded surface reaction layer is formed by ion sputtering or evaporation. It will be stripped off. As described above, the reactive ion etching method is a process in which a chemical action and a physical action occur simultaneously. Therefore, selectivity of etching only a specific substance can be obtained, and at the same time, anisotropy of cutting into the surface of the processing target substance perpendicularly can be obtained.

[0005] On the other hand, however, no effective reactive ion etching method has been found for magnetic materials for a long time. In practice, wet etching methods and argon ion milling methods have been used for magnetic materials. Thin-film magnetic heads, magnetic sensors, micro-transformers and the like are manufactured by these methods. Such a situation in a magnetic material significantly slows down the direction of miniaturization and high-density integration of a magnetic body as compared with a semiconductor, and has been an obstacle to development.

The reason that reactive ion etching of magnetic materials is difficult is that magnetic materials containing a transition metal element as a main component are all etching gases (for example, CF ₄ , CCl ₄ , etc.) which have been developed for semiconductor materials. CCl ₂ F
_{2, CClF 3, CBrF 3,} Cl 2, C 2 F 6, C 3
F ₈ , C ₄ F ₁₀ , CHF ₃ , C ₂ H ₂ , SF ₆ , SiF
₄ , BCl ₃ , PCl ₃ , SiCl ₄ , HCl, CHC
lF _2, etc.) is reacted with the magnetic material and the plasma, as compared with the reaction product of the semiconductor material, because it produces a much high bond energy material, less susceptible to sputtering effect, thus etching is not made .

Therefore, instead of analogy from semiconductor technology,
Efforts have been made to explore new reactive ion etching reactions, and recently the inventors of the present invention have developed carbon monoxide (CO).
A method using a mixed gas plasma of a gas and ammonia gas (NH ₃ ) has been invented. This method uses a transition metal carbonyl compound (Fe (C) on the surface of a magnetic material mainly composed of a transition metal element, which is a workpiece, by an active radical of CO.
_{O) 5, Ni (CO)} 4, Co 2 (CO) 8, Mn
₂ (CO) ₁₀ , Cr (CO) ₆ , V (CO) ₆ , Mo
(CO) ₆ , W (CO) ₆ ), and by evaporation in vacuum or sputtering by ions,
The principle is that they are stripped and etched. Transition metal carbonyls are the only compounds having a low binding energy among transition metals. However, in the plasma, the CO gas is decomposed into CO ₂ and C by a non-uniform reaction, so that the introduced CO gas does not contribute to the reaction, and the released C atoms react with the transition metal element to form a stable transition. Usually, no etching reaction takes place because it produces metal carbide. NH ₃ gas exhibits the property of delaying the above-mentioned non-uniformity reaction in the presence of a transition metal element, and the desired reactive ion etching proceeds in a plasma of a gas in which CO gas and NH ₃ gas are mixed in substantially equal amounts. I do.

It has been confirmed that reactive ion etching of a magnetic material such as permalloy (Fe—Ni alloy), Co—Cr alloy, or Fe is realized by a method based on this principle. As described above, an excellent reactive ion etching method for a magnetic material has been found, and technological development in the future is expected. In this method, processing of a fine figure and processing of an anisotropic shape are required. It is possible, but the etching speed is
For example, there is a problem that it is not as fast as 34 nm / min.

Accordingly, an object of the present invention is to provide an improved new technical means capable of realizing efficient reactive ion etching of a magnetic material at a higher etching rate.

[0010]

Means for Solving the Problems An object of the present invention is to provide a dry etching apparatus which solves the above-mentioned problems, wherein a part or all of a reaction vessel and metal parts in the reaction vessel are made of titanium. , Aluminum, or one or more metals selected from the group of alloys containing each or both of them as main constituent components. provide.

Further, the invention of this application relates to the above-mentioned apparatus, wherein a part or all of the reaction vessel and parts in the reaction vessel are formed of one or more of the above-mentioned metals in an exposed surface layer. (Claim 2), the support for supporting the substance to be etched is made of one or more of the above metals (claim 3), a high-frequency electrode, a high-frequency antenna, a ground electrode, a zero potential shield, One of the aspects is that one or more components of the deposition-preventing plate are made of the one or more metals.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a prior art reactive ion etching apparatus, a reaction vessel and components inside the reaction vessel are mainly made of stainless steel. Stainless steel is an alloy containing transition metals such as iron, nickel and chromium as main component elements, and has a composition close to that of a magnetic material. For this reason, when performing a reactive ion etching using a mixed gas plasma of the above CO gas and NH ₃ gas on a magnetic alloy containing a transition metal as a main component using a conventional reactive ion etching apparatus, etching is performed. At the same time as the target substance is etched, the reaction vessel, the electrode, the member holding the target substance, and all the members in contact with the plasma around the reaction container are subjected to the etching action. Therefore, the inside of the reaction vessel is corroded, and at the same time, there occurs a problem that all of the generated reactive gas plasma does not effectively act on the etching target material. This causes a number of undesirable results, such as causing contamination of the etching target material and at the same time impairing the etching speed. In order to solve this problem, according to the invention of this application, titanium (T) is used in place of a conventional stainless steel for a reaction vessel and at least a part of constituent metal parts in the reaction vessel.
i), Ti alloy, aluminum (Al), Al alloy or titanium-aluminum alloy.

[0013] In this case, the definition of at least “part” means that CO gas and N 2
A portion which is susceptible to an etching action by plasma by a mixed gas of H ₃ gas or a mixed gas of CO gas and a gas of amines as a nitrogen-containing compound, which adversely affects large reactive ion etching; Alternatively, it is defined as a part. From this,
When actually constructing the equipment, the method for plasma generation and its introduction and various types of components to be installed in the vessel, including the reaction vessel body or its inner surface, gas introduction and exhaust systems, and etching It is understood that “part” or all of the substance is made of the above-described metal in consideration of the type and size of the substance.

For example, FIGS. 1, 2 and 3 show a parallel plate type plasma apparatus, an inductively coupled type plasma apparatus, and an electron cyclotron resonance type plasma apparatus as the above-mentioned systems. Except for non-metallic parts such as glass and cooling water, a part or all of the following parts or parts are made of Ti, Al, or their respective alloys, or alloys of both.

1 Reaction vessel 2 Deposition plate 3 Ground electrode 4 Support plate 5 High frequency electrode 6 Zero potential shield 7 Conductance control valve 8 Window flange or feedthrough flange 9 Reaction gas inlet 10 Viewing window 11 High frequency power supply 12 Cooling water 13 Coil Antenna 14 quartz window 15 solenoid coil 16 microwave waveguide Each of Ti, Al, Cu and conventional stainless steel was actually tested. As a result, a support, a high-frequency electrode, and a zero potential shield supporting a substance to be etched were obtained. The best operation and effect were obtained when all the metal members inside the reaction vessel such as the ground electrode, the support, the shutter, the bolt and the nut were made of Ti. That is, in the reactive ion etching process, the rate at which these members made of Ti are corroded and abraded is so small as to be hardly observable as compared with stainless steel, and permalloy (80% Ni-Fe alloy ) And 10% Cr—Co alloy are about four times faster at 120 nm / min 140 nm, respectively.
/ Min. Further, no re-adhesion of the contaminant to the substance to be etched was recognized, and etching of a sharp and accurate shape became possible. Note that the components that most significantly affect such effects are the support and the ground electrode that support the substance to be etched. In order to constitute the above-mentioned parts, Ti was suitable from the viewpoint of its excellent vacuum resistance, mechanical strength, and workability such as weldability, vacuum resistance, bending and cutting. Of course, in addition to pure Ti,
As long as the Ti alloy satisfies these conditions, various types may be used, and preferred are Ti-Pd alloy, Ti-T
a alloy, Ti-Al-Sn alloy, Ti-Al-V-Mo
Alloy, Ti-Al-Sn-Zr-Mo-Si alloy, Ti
-Al-Zr-Mo-Sn alloy, Ti-Al-V alloy,
Ti-Al-Sn-Zr-Mo alloy, Ti-Al-V-
Sn alloy, Ti-V-Cr-Al alloy and the like can be mentioned.

Pure Al also exhibited the same function and effect. In terms of weldability and strength, care was required in handling compared to Ti. Of course, in addition to pure Al, Al-Cu-X ₁ alloy (X ₁ is an additional element such as Si, Mn, Mg), Al-M
n-X ₂ alloy (X ₂ is Mg, added elements such as Si), Al
-Mg-X ₃ alloy (X ₃ is Zn, Si, Cr, Mn, M
g), an Al—Si—X ₄ alloy (X ₄ is Mg, Cu,
The same effect can be obtained even if Cr is used.

Pure Cu and alloys containing Cu as a main component did not show any remarkable effects as compared with stainless steel. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0018]

EXAMPLE 1 (Fine processing of Fe thin film) A parallel plate type reactive ion etching apparatus shown in FIG. 1 was used. All internal metal parts including the reaction vessel were made of pure Ti. As a sample for reactive ion etching, a thin film of 450 nm thick Fe was formed on a Corning 7059 glass substrate by sputtering, and a large number of minute Ti pads were formed as masks on the surface by electron beam lithography and lift-off. Was used. The sample was cooled to 13.56M with water cooling.
Hz was placed on the lower electrode to which a high frequency was applied, and the distance between the high frequency electrode and the ground electrode facing it was 35 mm. C
6.3 cc / min each of O gas and NH ₃ gas,
While supplying the reaction vessel at a flow rate of 6.8 cc / min, the inside of the reactor was evacuated by a turbo-molecular pump, and the inside was 5.7 × 1
The pressure was maintained at 0 ^-3 Torr. A high frequency of 3.7 W / cm ² per electrode unit area was applied to the lower electrode holding the sample, a glow discharge plasma of a CO—NH ₃ mixed gas was generated, and reactive ion etching was performed.

The etching time was 4.0 minutes. After the etching reaction, the step formed between the portion covered by the Ti pad used as the mask and the uncovered portion was repeatedly measured with a reflection interferometer to determine the amount of etching per unit time. The shape produced by the etching was observed with an electron microscope, and the etching was evaluated by focusing on the smoothness and sharpness of the steps and the presence or absence of a contaminant or a re-adhesion substance.

As a result, the etching speed for the Fe thin film was 90 nm / min. In addition, the radius of curvature is about 0.
A shape with a sharpness of 1 μm and a depth of 400 nm could be produced. Example 2 (Fine processing of permalloy (80% Ni-Fe) alloy thin film) Under the same conditions as in Example 1, reactive ion etching of an 80% Ni-Fe alloy was possible. The etching speed was 120 nm / min, and the etching shape was similarly good. Example 3 (Fine processing of 10% Cr-Co alloy) Reactive ion etching of 10% Cr-Co alloy was possible under the same conditions as in Example 1. The etching speed is 140nm / m
in and the shape of the etching was similarly good.

[0021]

As described above in detail, by using the reactive ion etching apparatus of the invention of this application, reactive ion etching using a CO-NH ₃ mixed gas plasma or the like for a magnetic alloy can be performed by a conventional reaction ion etching method. It becomes more effective than the case where a ionic ion etching apparatus is used. That is, the etching speed for the magnetic alloy is about four times under the same etching condition, which contributes to the improvement of the working efficiency. In addition, the substance to be etched is not contaminated in the etching process, and reattachment of the substance removed by the etching can be reduced to such an extent that no problem occurs. With the above-described effects, a fine magnetic head for magnetic recording, a micro transformer,
Micro magnetic element, magnetic sensor, magnetoresistive element,
It is possible to manufacture spin diodes, spin transistors, spin valve elements, spin valve magnetic memories, tunnel magnetoresistive elements, and the like. Further, a patterned magnetic recording medium of a future high-density magnetic recording medium can be manufactured.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view of a parallel plate type reactive ion etching apparatus showing one embodiment.

FIG. 2 is a configuration sectional view of an inductively coupled reactive ion etching apparatus showing one embodiment.

FIG. 3 is a configuration sectional view of an electron cyclotron resonance type reactive ion etching apparatus showing one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2 Deposition plate 3 Ground electrode 4 Support plate 5 High frequency electrode 6 Zero potential shield 7 Conductance control valve 8 Window flange or feed-through flange 9 Reaction gas inlet 10 Viewing window 11 High frequency power supply 12 Cooling water 13 Coiled antenna 14 Quartz window 15 Solenoid coil 16 Microwave waveguide

Claims (4)

(57) [Claims] 1. A dry etching apparatus, wherein a part or all of a reaction vessel and a metal part in the reaction vessel are made of titanium, aluminum, or an alloy containing each or both of them as a main component. A reactive ion etching apparatus comprising at least one metal selected from the group. 2. The reaction vessel and parts in the reaction vessel, a part or the whole of which is formed of the one or more metals in an exposed surface layer.
Reactive ion etching equipment. 3. The reactive ion etching apparatus according to claim 1, wherein the support for supporting the substance to be etched is made of one or more metals. 4. A high-frequency electrode, a high-frequency antenna, a ground electrode, a zero potential shield, and one or more components of a deposition-preventing plate are made of the one or more metals.
Or 2 reactive ion etching apparatus.