JP4332238B2 - Reactive ion etching method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reactive ion etching method and apparatus for etching a material on a semiconductor, an electronic component, or other substrate using plasma.
[0002]
[Prior art]
Various types of etching apparatuses used in the prior art are known, and one of them is a parallel plate type as shown in FIG. 4 of the accompanying drawings. In the vacuum chamber A, an anode B and a cathode, that is, a substrate electrode C are arranged to face each other, a reactive gas is introduced from the anode B, and a high-frequency power source E is connected to the substrate electrode C through a matching circuit D.
FIG. 5 shows another example of a parallel plate type etching apparatus. In this case, a high frequency power source G is also connected to the electrode B via a matching circuit F, and high frequency powers having different frequencies are applied to the upper and lower electrodes. Is done.
[0003]
FIG. 6 shows a conventional example of an ECR etching apparatus, in which μ waves are introduced from the upper part of the vacuum chamber A through the dielectric window B, and high-density plasma is formed by electron cyclotron resonance at a magnetic field of 875 Gauss.
[0004]
FIG. 7 shows an inductively coupled discharge etching apparatus in which an antenna B composed of a single coil for generating discharge plasma is provided in the vacuum chamber A outside the dielectric side wall A1 of the vacuum chamber A. High frequency power is applied to the antenna B from the plasma generating high frequency power source C, and an etching gas mainly composed of a halogen-based gas is introduced from the vicinity of the upper top plate A2 through the flow controller, and the gas is introduced into the vacuum chamber A. Then, the plasma is formed at a low pressure, the introduced gas is decomposed, and the generated atoms, molecules, radicals, and ions are actively used, and a high-frequency electric field is applied from the high-frequency power source E to the substrate electrode D in contact with the plasma. It is configured to etch the substrate placed on D.
FIG. 8 shows a modification of the structure shown in FIG. 7, in which the upper wall of the vacuum chamber A is mounted on a flat dielectric F to form a spiral antenna G to form inductively coupled plasma. . The method of FIG. 7 is called ICP (Inductively Coupled Plasma), and the method of FIG. 8 is called TCP (Transfer Coupled Plasma) for distinction.
[0005]
FIG. 9 shows a magnetic neutral wire discharge etching apparatus previously proposed by the present inventors in Japanese Patent Laid-Open No. 7-263192. In the previously proposed apparatus, a magnetic neutral line E is formed inside the vacuum chamber A by three magnetic field coils B, C, D placed outside the dielectric cylindrical wall A1 at the top of the vacuum chamber A. A configuration in which a ring-shaped plasma is formed by applying a high-frequency electric field from the antenna high-frequency power source G to the single antenna F disposed inside the intermediate magnetic field coil C along the magnetic neutral line E. Has been. Further, the etching gas is introduced from the vicinity of the upper top plate A2 through the flow controller, and the pressure is controlled by the opening ratio of the contact valve. A high frequency power is applied to the substrate electrode H below the vacuum chamber A from a bias high frequency power source I.
[0006]
As a representative example, the ICP etching shown in FIG. 7 will be described.
The etching gas is introduced from the vicinity of the upper flange, and high frequency power is applied from the high frequency power source C to the antenna B installed outside the dielectric cylindrical partition wall A1 to form plasma, and the introduced gas is decomposed. At this time, since the distribution of the plasma and the introduced gas is required to be uniform on the substrate, a shower plate having a large number of holes is generally provided in the upper flange, and the gas is introduced into the vacuum chamber A through it. Is done. If the gas flow is uniform and the plasma density and potential are uniform, the density distribution of etchants (radicals and ions) generated in the plasma is uniform, and the substrate is uniformly etched. By the way, plasma density and potential uniformity in ICP etching are greatly influenced by the chamber structure and pressure. When the chamber structure is determined, the pressure condition for obtaining uniformity is almost uniquely determined, and the selection range of the condition is extremely narrow.
[0007]
On the other hand, in the magnetic neutral discharge (NLD) etching apparatus of FIG. 9, the plasma neutral density and potential can be controlled in a low pressure gas region where the position of the magnetic neutral line can be freely changed and ICP is not generated. Therefore, conditions with good etching uniformity can be set easily.
[0008]
[Problems to be solved by the invention]
However, devices have become denser and the processing width has become finer, and it has become impossible to cope with the ultra-fine process by the conventional method of determining the etching conditions by setting the etching conditions by trial and error. In etching, the substrate material is irradiated with highly reactive radicals and ions and gasified by the reaction with the substrate material to etch the substrate material. However, the etching is not necessarily performed, and shape control is also required. For example, when the processing width is wider than 0.3 μm, the accuracy required for the gas mixture ratio is not so strict, but when it is narrower than 0.3 μm, precise control of the gas mixture ratio is required. However, when precise control of the mixing ratio is performed, there is no index for determining the mixing ratio, and trial and error experiments are repeatedly performed and the etching shape is determined after observing with an electron microscope. For this reason, much time has been spent until ultrafine processing conditions are obtained.
[0009]
Examples of materials used as an auxiliary etching gas for etching oxide films include argon, hydrogen, and carbon monoxide. Etching main gases include CF ₄ , C ₃ F ₈ , and C ₄ F _8. CHF ₃ , CH ₂ F _{2 and the} like are also used as etching main gases. The main etching gas decomposes as the plasma density increases or the residence time in the plasma increases, and a large amount of radicals such as CF, CF ₂ , CF ₃ , and CHF ₂ that are adhesive substances are generated. Ar as an etching auxiliary gas plays a role of diluting the concentration of radical species to an appropriate concentration. In addition, the film adhering to the side and bottom of the etching portion is activated by sputtering or ion bombardment to form a substrate material. It is thought to play a role in promoting etching reaction and adjusting the etching shape.
[0010]
In addition, hydrogen gas decomposes in plasma to form hydrogen atoms, reacts with CF, CF ₂ radicals, etc., and changes to substances with weak adhesion and forms polymerization precursors such as CH ₂ , CF ₂ , CHF. In addition, it is considered to be a substance that adheres to the upper part of the resist or the side wall or bottom of the etched part and affects the etching shape. It is also considered that when hydrogen atoms adhere to the surface of the etched portion, it forms a —C—H or one Si—H bond on the surface, thereby suppressing the adhesion of radicals.
In any case, since the detailed mechanism of etching is not known, trial and error experiments are currently required, and it is necessary to reduce the time for analyzing the results and determining the process conditions by trial and error.
[0011]
Therefore, the present invention solves the above-mentioned problems, enables the gas cross-section to be precisely controlled to optimize the cross-sectional shape of the etching, and the reactive ion etching method and apparatus capable of dealing with fine processing of 0.3 μm width or less. The purpose is to provide.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a magnetic neutral wire discharge etching apparatus is used, and a mass spectrometer is provided in the vicinity of a substrate electrode so that ion species generated in plasma can be observed. The mixture ratio is set so that the peak intensity of CHF ₂ ⁺ ions becomes the maximum value from the dependence on the mixture ratio.
That is, using a magnetic neutral line discharge device that can form plasma in a region where the plasma density is not higher than necessary, at least one gas containing hydrogen was mixed as a gas species, and the correlation between etching conditions and ion species was investigated. . As a result, it was found from the dependence on the mixing ratio that the etching can be performed vertically even with an ultrafine pattern when the etching conditions (mixing ratio in this case) are determined so that the peak intensity of CHF ₂ ⁺ ions becomes the maximum value. This is probably because the ratio of the etchant substance and the adhesive substance that reaches the substrate is optimal near the etching conditions in which CHF ₂ ⁺ ions peak, and the etching shape can be easily controlled.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
According to one embodiment of the present invention, there is provided magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously existing in the vacuum chamber, and the magnetic neutral line is provided with the magnetic neutral line. A plasma generator comprising a plurality of high frequency coils including a single layer for generating a discharge plasma on this magnetic neutral wire by applying an alternating electric field along the line is provided, and a gas mainly composed of a halogen-based gas is placed in a vacuum. introduced into, and decomposing the introduced gas to form a plasma at low pressure, generated atoms, molecules, radicals, ions and take advantage, on the substrate electrode by applying an alternating electric field or radio-frequency electric field to the substrate electrode in contact with the plasma in the reactive ion etching method of etching a substrate placed, place the mass spectrometer in the vicinity of the substrate electrode, ions and C by monitoring the various ions generated in the plasma ₂ F ₂ relative values of the peak intensities of C HF 2 ₊ ions from the relationship between the flow rate dependence determined gas mixture ratio which is an etching condition such that the maximum, the gas flow control device such that the gas mixture ratio It is characterized in that the etching cross-sectional shape is optimized by controlling.
[0014]
Etching conditions consists et or gas mixing ratio, the relative values of the peak intensity of CHF 2 ₊ ions may be set gas mixing ratio so as to maximize.
Further, one kind of gas used by mixing can be composed of hydrogen gas or fluorocarbon gas containing hydrogen.
[0015]
According to another embodiment of the present invention, there is provided magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously existing in the vacuum chamber, and the magnetic neutral line is provided with the magnetic neutral line. A plasma generator having a plurality of high-frequency coils including a single layer for generating a discharge plasma on this magnetic neutral wire by applying an alternating electric field along the vacuum is used to evacuate a gas mainly composed of a halogen-based gas. introduced into, and decomposing the introduced gas to form a plasma at low pressure, generated atoms, molecules, radicals, and take advantage of the ions, on the substrate electrode by applying an alternating electric field or radio-frequency electric field to the substrate electrode in contact with the plasma In the reactive ion etching apparatus that etches the substrate placed on the substrate, a mass spectrometer that monitors various ions generated in the plasma is provided near the substrate electrode, and this mass Strength of various ions from the output of the analyzers is determined etching conditions such as the relative value of the peak intensity of CHF 2 ₊ ions from the relationship with respect to CH ₂ F ₂ gas mixture ratio is maximized is set to the etching conditions An etching condition setting means is provided.
[0016]
【Example】
Embodiments of the present invention will be described below with reference to FIGS.
FIG. 1 shows an example of a reactive ion etching apparatus implementing the present invention. In the illustrated etching apparatus, reference numeral 1 denotes a vacuum chamber, which is provided with a cylindrical dielectric side wall 2 at the top thereof, and a magnetic field generation for forming a magnetic neutral line in the vacuum chamber 1 outside the dielectric side wall 2. Three magnetic field coils 3, 4, 5 constituting the means are provided, and a magnetic neutral wire 6 is formed in the upper part of the vacuum chamber 1.
Between the intermediate magnetic field coil 4 and the outside of the dielectric side wall 2, a multiple high frequency coil 7 for generating plasma including a single layer is arranged, and this high frequency coil 7 is connected to a high frequency power source 8 and three magnetic field coils. An alternating electric field is applied along the magnetic neutral line 6 formed in the upper part of the vacuum chamber 1 by 3, 4, and 5 to generate discharge plasma in the magnetic neutral line.
The top plate 9 at the top of the vacuum chamber 1 is hermetically fixed to the top flange of the dielectric side wall 2, and the top plate 9 is provided with a shower plate 10 for introducing an etching gas, which is not shown. It is connected to an etching auxiliary gas source.
[0017]
A substrate electrode 11 is also arranged in the vacuum chamber 1 as shown in the figure, and this substrate electrode 11 is connected to a bias high-frequency power source 13 via a matching capacitor 12. A mass analyzer 14 for observing ion species generated during etching is attached to the side wall of the vacuum chamber 1 in the vicinity of the substrate electrode 12, and the output of the mass analyzer 14 is connected to a computer 15. The computer 15 calculates a mixing ratio at which the peak intensity of CHF ₂ ⁺ ions is maximum by data analysis. Data calculated by the computer 14 is input to a gas flow controller (not shown) and is configured to control the flow rate of the etching gas introduced through the shower plate 10 in the top plate 9. Yes. Thereby, the etching conditions for the ultrafine pattern can be set.
In FIG. 1, 16 is an exhaust port connected to an exhaust system (not shown).
[0018]
The operation of the illustrated apparatus configured as described above will be described.
1 is used, the power of the plasma generating high frequency power supply 8 is 1.0 KW, the power of the substrate bias high frequency power supply 13 is 500 W, the pressure of the vacuum chamber 1 is 3 mTorr, the flow rate of C ₄ F ₈ and CH ₂ F _2. FIG. 2 shows the CH ₂ F ₂ flow rate dependence of each ion species in the plasma when the sum of the flow rates of 5 Osccm. In this example, when the flow rate of CH ₂ F ₂ is 20 sccm, the peak intensity of CHF ₂ ⁺ ions is maximized. At this time, as shown in FIG. 3, a groove of the oxide film is vertically formed at a depth of about 800 nm along the resist pattern having a width of 20 nm formed on the oxide film. At this time, the etching rate of the silicon oxide film was about 550 nm / min.
Conventionally, when such ultrafine groove processing is performed, a large amount of plasma parameters are required, and thus, a great amount of labor is required to obtain etching conditions. According to the present invention, as described above, the mass analyzer 13 Is used to observe the ion species generated during the etching, and the measurement data is analyzed by the computer 14 to calculate the mixing ratio at which the peak intensity of CHF ₂ ⁺ ions reaches the maximum value. By controlling the flow rate of the etching gas introduced through the shower plate 10 in the top plate 9, the etching conditions for the ultrafine pattern can be set.
[0019]
In the illustrated embodiment, an example in which the present invention is applied to an NLD etching apparatus has been described. Needless to say, the same effect can be expected when applied to an NLD plasma CVD apparatus.
[0020]
【The invention's effect】
As described above, according to the present invention, a magnetic neutral line discharge etching apparatus is used, and a mass spectrometer is provided in the vicinity of the substrate electrode so that ion species generated in the plasma can be observed, and the mixing ratio Because the mixing ratio is set so that the peak intensity of CHF ₂ ⁺ ions is maximized due to the dependence, process conditions can be constructed without trial and error, so it can be used for microfabrication with a width of 0.3 μm or less. The dry etching which can be performed became easy. Therefore, it becomes possible to greatly contribute to the reactive ion etching process used for processing semiconductors and electronic parts.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing one embodiment of the present invention.
2 is a graph showing the CH ₂ F ₂ flow rate dependence of each ion species in plasma measured using the apparatus of FIG. 1;
3 is an electron micrograph showing a state in which a groove of an oxide film is formed vertically along a resist pattern having a width of 20 nm formed on the oxide film using the apparatus of FIG.
FIG. 4 is a schematic diagram showing an example of a conventional parallel plate etching apparatus.
FIG. 5 is a schematic diagram showing a conventional tripolar etching apparatus.
FIG. 6 is a schematic diagram showing a conventional ECR etching apparatus.
FIG. 7 is a schematic diagram showing a conventional inductively coupled etching apparatus.
FIG. 8 is a schematic diagram showing a conventional transfer coupled etching apparatus.
FIG. 9 is a schematic diagram showing a conventional magnetic neutral discharge type etching apparatus.
[Explanation of symbols]
1: Vacuum chamber 2: Cylindrical dielectric side wall 3: Magnetic field coil 4: Magnetic field coil 5: Magnetic field coil 6: Magnetic neutral wire 7: High frequency coil 8: High frequency power source 9 for plasma generation 9: Top plate
10: Shower plate
11: Board electrode
12: Matching capacitor
13: Bias high frequency power supply
14: Mass spectrometer
15: Computer
16: Exhaust port

Claims (4)

A magnetic field generating means for forming an annular magnetic neutral line that is continuously present in the vacuum chamber and having a zero magnetic field is provided, and an alternating electric field is applied along the magnetic neutral line to add the magnetic neutral line. A plasma generator is provided with multiple high-frequency coils including a single layer for generating discharge plasma, and a gas mainly composed of a halogen-based gas is introduced into a vacuum to form a plasma at a low pressure. decomposing a gas, generated atoms, molecules, radicals, ions and take advantage, to apply an alternating electric field or radio-frequency electric field to the substrate electrode in contact with the plasma to etch the substrate placed on the substrate electrode reactive ion etching In the method, a mass spectrometer is arranged in the vicinity of the substrate electrode, and various ions generated in the plasma are monitored. From the relationship between the ions and the CH ₂ F ₂ flow rate dependence, C Seeking gas mixing ratio relative values of the peak intensity of the HF 2 ₊ ions are etching conditions such that the maximum, to optimize the etching cross-sectional shape by controlling the gas flow control device such that the gas mixture ratio A reactive ion etching method characterized by that.   2. The reactive ion etching method according to claim 1, wherein one of the gases used by mixing is hydrogen gas or a fluorocarbon gas containing hydrogen. A magnetic field generating means for forming an annular magnetic neutral line that is continuously present in the vacuum chamber and having a zero magnetic field is provided, and an alternating electric field is applied along the magnetic neutral line to add the magnetic neutral line. Has a plasma generator comprising a plurality of high frequency coils including a single layer for generating discharge plasma, and a gas mainly composed of a halogen-based gas is introduced into a vacuum to form a plasma at a low pressure. decomposing the introduced gas, generated atoms, molecules, radicals, ions and take advantage, reactive ion etching the substrate placed on the substrate electrode by applying an alternating electric field or radio-frequency electric field to the substrate electrode in contact with the plasma in the etching apparatus, in the vicinity of the substrate electrode, a mass spectrometer to monitor the various ions generated in the plasma is provided, the strength of the various ions from the output of the mass spectrometer CH ₂ F ₂ relationship sought etching conditions such as the relative value of the peak intensity of CHF 2 ₊ ions is maximized by having with respect to the gas mixing ratio, in that a etching condition setting means for setting to the etching conditions Characteristic reactive ion etching equipment. 4. The reactive ion etching apparatus according to claim 3 , wherein one of the gases used by mixing is hydrogen gas or a fluorocarbon gas containing hydrogen.

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