JP2000021857A - Method and device for reactive ion etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control processing shape and thickness highly precisely by providing a mass spectrometer near a substrate electrode, observing ionic species generated in plasma and detecting an etching final point from time variation with time of peak intensity of CHF2+ ion, etc. SOLUTION: A substrate electrode 11 is arranged inside a vacuum chamber 1 and the substrate electrode 11 is connected to a bias high frequency power supply 13 through a matching capacitor 12. A mass spectrometer 14 attached to a side wall of the chamber 1 observes ionic species generated during etching. Output of the spectrometer 11 is input to a computer 15 and variation with time of peak intensity of CHF2+ ion etc., is calculated by data analysis. The calculated data is input to a high frequency power supply control device and a high frequency power supply 8 of a high frequency coil 7 is controlled and discharge is finished after detection of an etching final point by the computer 15. Thereby, processing shape and thickness can be controlled highly accurately.

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 method and apparatus for etching semiconductors, electronic parts, optical parts, and other substances on a substrate using plasma.

[0002]

2. Description of the Related Art Various types of etching apparatuses have been used in the prior art, one of which is a parallel plate type as shown in FIG. 4 of the accompanying drawings. An anode B and a cathode, that is, a substrate electrode C, are arranged in a vacuum chamber A so as to face each other, a reaction gas is introduced from the anode B, and a high-frequency power source E is connected to the substrate electrode C via a matching circuit D. FIG. 5 shows another example of a parallel plate type etching apparatus for etching an oxide film. In this case, a high frequency power source G is also connected to an electrode B via a matching circuit F, and upper and lower electrodes are connected to the upper and lower electrodes. Different high frequency power is applied.

FIG. 6 shows a conventional example of an ECR etching apparatus, in which a microwave is introduced from the upper part of a vacuum chamber A through a dielectric window B, and a high-density plasma is formed by electron cyclotron resonance in a magnetic field of 875 Gauss. .

FIG. 7 shows an inductively coupled discharge etching apparatus in which an antenna B composed of a single coil for generating discharge plasma in a vacuum chamber A is provided outside a dielectric side wall A1 of the vacuum chamber A. A high-frequency power is applied to the high-frequency antenna B from a high-frequency power source C for plasma generation, an etching gas mainly composed of a halogen-based gas is introduced from around the upper top plate A2 through a flow rate controller, and the gas is removed from the vacuum chamber A. To form a plasma at a low pressure, decompose the introduced gas, actively use the generated atoms, molecules, radicals, and ions, and apply a high-frequency electric field from a high-frequency power source E to a substrate electrode D in contact with the plasma. The substrate mounted on the substrate electrode D is etched. FIG. 8 is a modification of the one shown in FIG. 7, in which the upper wall of the vacuum chamber A is formed of a flat dielectric F, and a spiral antenna G is mounted thereon to form inductively coupled plasma. It is configured. FIG.
Is referred to as ICP (Inductively Coupled Plasma), and the method in FIG. 8 is referred to as TCP (Transfer Coupled Plasma) for distinction.

FIG. 9 shows that the inventors of the present application disclosed in
1 shows a magnetic neutral discharge etching apparatus proposed in Japanese Patent No. 263192. The device proposed earlier is a vacuum chamber A
A magnetic neutral line E is formed inside the vacuum chamber A by the three magnetic field coils B, C, and D mounted on the outside of the dielectric cylindrical wall A1 on the upper side of the magnetic neutral line E. A ring-shaped plasma is formed by applying a high-frequency electric field from a high-frequency power source for antenna G to a single antenna F disposed inside the magnetic field coil C of the first embodiment. The etching gas is introduced from around the upper top plate A2 through the flow controller, and the pressure is controlled by the aperture ratio of the contactance valve. High frequency power is applied from a high frequency power source I for bias to a substrate electrode H below the vacuum chamber A.

As a typical example, the ICP etching shown in FIG. 7 will be described. The etching gas is introduced from the vicinity of the upper flange, and a high-frequency power is applied from a high-frequency power source C to an antenna B provided 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, generally, a shower plate having a large number of holes is provided on an upper flange, through which gas is introduced into the vacuum chamber A. 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 becomes uniform, and the substrate is etched uniformly. Incidentally, the uniformity of the plasma density and the potential in the ICP etching is greatly affected by the chamber structure and the pressure. Once the chamber structure is determined, the pressure conditions for obtaining uniformity are almost uniquely determined, and the range of conditions to be selected is extremely narrow.

On the other hand, in the magnetic neutral ray discharge (NLD) etching apparatus shown in FIG. 9, the position of the magnetic neutral ray can be freely changed.
In addition, since the plasma density and potential can be controlled in a low-pressure gas region where ICP does not occur, conditions with good etching uniformity can be easily set.

[0008]

However, as the device density increases, the processing width and processing thickness become finer, and a method of setting an etching end point with a previously determined etching time as in the prior art and performing a process. Then, it became impossible to cope with the ultrafine processing. In etching, the substrate material is gasified and etched by irradiating the substrate with radicals and ions having high reactivity and reacting with the substrate material. However, it is not only necessary to simply cut, but also the shape and thickness need to be controlled. For example, when a micromachine is formed on a glass substrate by an etch-back process, the resist pattern is transferred to the glass substrate with the selectivity between the resist and the glass substrate (etching rate ratio) being within twice, but the selectivity is low. Endpoint detection is important. If the etching is continued even after the resist disappears, the desired shape and thickness cannot be obtained. In addition, if the process is completed before the resist is completely etched, there is a resist residue on the glass surface, and a desired function cannot be obtained. Therefore, in a process such as an etch-back process, the end point must be detected with high accuracy because the selectivity between the resist and the substrate is small.

Accordingly, an object of the present invention is to provide a reactive ion etching method and apparatus capable of solving the above problems and detecting the etching end point with high accuracy and controlling the processing shape and thickness with high accuracy. I have.

[0010]

According to the present invention, in order to achieve the above object, the selectivity between the substrate and the resist is 1 to 1.
In the reactive ion etching for performing the etching in the range of 2, a mass spectrometer is provided near the substrate electrode,
The ion species generated in the plasma can be observed, and the end point of the etching can be detected from the temporal change of the peak intensity of CHF ₂ ⁺ ions and the like.

That is, when parts of a micromachine or optical parts are formed on a glass substrate by etching,
Gases such as argon and carbon monoxide are used as an etching auxiliary gas, and CF ₄ , C ₃ F
₈ , C ₄ F _{8 and the} like are used. The main etching gas is
When the plasma density increases or the residence time in the plasma increases, the decomposition proceeds, and CF, CF
₂ , a large amount of radicals such as CF ₃ are generated. Ar as an etching auxiliary gas not only plays a role of diluting the concentration of radical species to an appropriate concentration, but also sputters a film attached to the side and bottom of the etched portion or activates the film by ion bombardment and reacts with the substrate material. It is thought that it plays a role in promoting the reaction of (1) and adjusting the etching shape. In any case, since the detailed mechanism of etching is not known, trial and error experiments are currently required. In addition, when a component such as a micromachine or an optical component is manufactured by etch-back, etching is performed with a small selectivity to a resist, so that the end point must be detected with high accuracy.

For this reason, whether a high-precision etching end point can be detected by installing a mass spectrometer near the substrate using a magnetic neutral discharge device capable of forming plasma in a region where the plasma density is not unnecessarily high. The correlation with ion species was investigated. As a result, it was found that the end point could be detected with high accuracy by observing the change in the peak intensity of COF ⁺ , CF ₂ ⁺ and CHF ₂ ⁺ ions. H contained in CHF ₂ ions originates from —CHx contained in the resist, and when the resist disappears, the peak of CHF ₂ ⁺ ions decreases to a background level. The CF ₂ ⁺ ions are considered to originate from CF ₂ radicals, and as the resist decreases, the reaction between the CF ₂ and the resist disappears, so that the CF ₂ ⁺ increases as a result.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to one embodiment of the present invention, a plasma generator for generating plasma is provided in a vacuum chamber, and a gas mainly composed of a halogen-based gas is introduced into a vacuum, and A plasma is formed at the same time, the introduced gas is decomposed, and the generated atoms, molecules, radicals, and ions are used, and an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma, and the substrate placed on the substrate electrode is removed. ,
In a reactive ion etching method in which etching is performed within a selection ratio of a substrate and a resist within a range of 1 to 2, a mass spectrometer is arranged near a substrate electrode and CH generated in plasma is formed.
Various ions including F ₂ ⁺ are monitored, and a final check is made based on a time change of the peak intensity including CHF ₂ ⁺ ions, and the power supply control device of the plasma generator is controlled based on the detected signal to terminate the discharge. You.

According to another embodiment of the present invention, there is provided a magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in a vacuum chamber, and the magnetic neutral line. A plasma generator consisting of multiple high-frequency coils including a single layer for generating a discharge plasma in this magnetic neutral line by applying an alternating electric field along To form plasma at low pressure and decompose the introduced gas to generate atoms,
A substrate placed on the substrate electrode by applying an alternating electric field or a high-frequency electric field to the substrate electrode in contact with the plasma by positively utilizing the molecules, radicals, and ions, within a selection ratio of the substrate and the resist of 1 to 2. In a reactive ion etching method in which etching is performed by a method, a mass spectrometer is arranged near a substrate electrode, and various kinds of ions including CHF ₂ ⁺ generated in plasma are monitored, and a time change of a peak intensity including CHF ₂ ⁺ ions is performed. From the terminal inspection, the power supply control device of the plasma generator is controlled based on the detected signal to terminate the discharge.

The present method can be used in a step of etching back the applied resist mask and transferring the pattern.

According to yet another embodiment of the present invention,
The reactive ion etching device is provided with a plasma generating device that generates plasma in a vacuum chamber, introduces a gas mainly composed of a halogen-based gas into a vacuum, forms plasma at a low pressure, and decomposes the introduced gas, Utilizing the generated atoms, molecules, radicals, and ions, an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma, and the substrate mounted on the substrate electrode has a selectivity of substrate and resist of 1
While being configured to etch within the range of ~ 2,
In the vicinity of the substrate electrode, a mass spectrometer for monitoring various ions including CHF ₂ ⁺ generated in the plasma is provided, and an end point for detecting an end point from a time change of a peak intensity including the CHF ₂ ⁺ ion from an output of the mass spectrometer. Detecting means is provided, and the power supply control device of the plasma generator is controlled based on the signal detected by the end point detecting means to terminate the discharge. Preferably, the plasma generating apparatus for generating plasma in the vacuum chamber includes a magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in the vacuum chamber, And a plurality of high frequency coils, including a single coil, for applying an alternating electric field along the line to generate a discharge plasma in the magnetic neutral line.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an example of a reactive ion etching apparatus embodying 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 an upper portion thereof, and a magnetic field generation for forming a magnetic neutral line in the vacuum chamber 1 is provided outside the dielectric side wall 2. Three magnetic field coils 3 constituting the means,
4 and 5 are provided to form a magnetic neutral wire 6 in the upper portion of the vacuum chamber 1. Intermediate magnetic field coil 4 and dielectric side wall 2
A high-frequency coil 7 for generating multiple plasmas including a single layer is disposed between the high-frequency coil 7 and the high-frequency power supply 8. An alternating electric field is applied along the magnetic neutral line 6 formed on the upper portion 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 upper flange of the dielectric side wall 2,
The top plate 9 is provided with a shower plate 10 for introducing an etching gas, and the shower plate 10 is connected to an etching auxiliary gas source (not shown).

A substrate electrode 11 is disposed in the vacuum chamber 1 as shown in the figure. The substrate electrode 11 is connected to a bias high-frequency power supply 13 via a matching capacitor 12. Vacuum chamber 1 near substrate electrode 12
A mass spectrometer 14 for observing ion species generated during etching is attached to the side wall of the mass spectrometer.
The output of 14 is connected to a computer 15, and the computer 15 calculates the time change of the peak intensity of CHF ₂ ⁺ ions and the like by data analysis. The data calculated by the computer 14 is input to a high-frequency power supply control device (not shown), which controls the high-frequency power supply 8 of the high-frequency coil 7 so that the computer 15 detects the end point of the etching and ends the discharge. . In FIG. 1, 16
Denotes an exhaust port connected to an exhaust system (not shown).

The operation of the illustrated apparatus configured as described above will be described. Using the apparatus shown in FIG. 1, CHF ₂ ⁺ when the power of the plasma generating high frequency power supply 8 was 1.0 KW, the power of the substrate bias high frequency power supply 13 was 500 W, the pressure of the vacuum chamber 1 was 2 mTorr, and the flow rate of CF ₄ was 5 Osccm. FIGS. 2 and 3 show changes of CF ₂ ⁺ and CF ₂ ⁺ ions depending on the etching time. In this example, when the etching time is 17 minutes, the etching is completed, and the peak intensity of CHF ₂ ⁺ ions is minimized and does not change. Similarly, as shown in FIG. 3, the time change of CF ₂ ⁺ conversely increases with time, reaches a maximum at 17 minutes, and does not change. Conventionally, when processing a microlens or the like by such an etch back, a time when an end point is obtained is obtained in advance, and discharge is ended when a set time is reached. This is because when the plasma density is low and the etching rate is low, some time deviation is allowed. However, when etching with high-density plasma, highly accurate endpoint detection is required, which can be achieved by practicing the present invention.

In the illustrated embodiment, an example in which the present invention is applied to an NLD etching apparatus has been described. However, the present invention can be similarly applied to other types of etching apparatuses. Further, in the illustrated embodiment, the case where the present invention is applied to processing of a micromachine component or an optical component has been described.
Needless to say, similar effects can be expected when applied to other processing.

[0021]

As described above, according to the present invention, in the reactive ion etching in which the selection ratio between the substrate and the resist is in the range of 1-2, the mass spectrometer is placed near the substrate electrode. It is possible to observe the ion species generated in the plasma and to detect the etching end point from the time change of the peak intensity of CHF ₂ ⁺ ion etc. Can be controlled. As a result, semiconductors and electronic components,
It can greatly contribute to the reactive ion etching process used for processing glass and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a graph showing the time dependence of CHF ₂ + intensity in plasma measured using the apparatus of FIG. 1;

FIG. 3 is a graph showing the time dependence of CF ₂ intensity in plasma measured using the apparatus of FIG. 1;

FIG. 4 is a schematic diagram showing an example of a conventional parallel plate type etching apparatus.

FIG. 5 is a schematic diagram showing a conventional triode 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-coupling type etching apparatus.

FIG. 9 is a schematic diagram showing a conventional magnetic neutral beam discharge etching apparatus.

[Explanation of symbols]

 1: vacuum chamber 2: cylindrical dielectric side wall 3: magnetic field coil 4: magnetic field coil 6: magnetic neutral wire 7: high frequency coil 8: high frequency power supply for plasma generation 9: top plate 10: shower plate 11 ： Substrate electrode 12 ： Matching condenser 13 ： Bias RF power supply 14 ： Mass analyzer 15 ： Computer 16 ： Exhaust port

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K057 DA14 DD03 DE06 DJ06 DN01 DN03 5F004 AA01 BA08 BB07 BB11 BC08 CA02 CA03 CA06 CB04 CB15 DA01 DB26 EA27

Claims (6)

[Claims] 1. A plasma generator for generating plasma in a vacuum chamber is provided, a gas mainly composed of a halogen-based gas is introduced into a vacuum, plasma is formed at a low pressure, and the introduced gas is decomposed and generated. Utilizing atoms, molecules, radicals, and ions, an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma, and the substrate placed on the substrate electrode is selected within a selection ratio of the substrate and the resist of 1 to 2. In the reactive ion etching method for etching, a mass spectrometer is arranged near a substrate electrode, and various ions including CHF ₂ ⁺ generated in plasma are monitored to detect CH.
A reactive ion etching method comprising: performing a final inspection based on a time change of a peak intensity including F ₂ ⁺ ions; and controlling a power supply control device of a plasma generator based on a detected signal to terminate discharge. 2. The reactive ion etching method according to claim 1, wherein the applied resist mask is used in a step of etching back the pattern and transferring the pattern. 3. A magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in a vacuum chamber, and applying an alternating electric field along the magnetic neutral line to generate the magnetic field. Provide a plasma generator consisting of a single high-frequency coil and a single high-frequency coil for generating discharge plasma on the neutral wire, and introduce a gas mainly composed of halogen-based gas into vacuum to form plasma at low pressure. At the same time, the introduced gas is decomposed, and the generated atoms, molecules, radicals, and ions are positively used, and the substrate placed on the substrate electrode by applying an alternating electric field or a high-frequency electric field to the substrate electrode in contact with the plasma,
In a reactive ion etching method in which a substrate and a resist are etched within a selection ratio of 1 to 2, a mass spectrometer is arranged near a substrate electrode to monitor various ions including CHF ₂ ⁺ generated in plasma. CH
A reactive ion etching method comprising: performing a final inspection based on a time change of a peak intensity including F ₂ ⁺ ions; and controlling a power supply control device of a plasma generator based on a detected signal to terminate discharge. 4. The reactive ion etching method according to claim 3, wherein the applied resist mask is used in a step of etching back the pattern and transferring the pattern. 5. A plasma generator for generating plasma in a vacuum chamber is provided, a gas mainly containing a halogen-based gas is introduced into a vacuum, plasma is formed at a low pressure, and the introduced gas is decomposed and generated. Utilizing atoms, molecules, radicals, and ions, an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma, and the substrate placed on the substrate electrode is selected within a selection ratio of the substrate and the resist of 1 to 2. While being configured to be etched, near the substrate electrode,
A mass spectrometer for monitoring various ions including CHF ₂ ⁺ generated in the plasma is provided, and end point detecting means for detecting an end point from a time change of a peak intensity including CHF ₂ ⁺ ions from an output of the mass spectrometer is provided. A reactive ion etching apparatus characterized in that a power supply control device of a plasma generator is controlled based on a signal detected by an end point detecting means to terminate discharge. 6. A plasma generating apparatus for generating plasma in a vacuum chamber includes: a magnetic field generating means for forming an annular magnetic neutral line at a position of zero magnetic field continuously present in the vacuum chamber; 5. The reactive element according to claim 4, further comprising a single high frequency coil including a single coil for applying an alternating electric field along the neutral line to generate a discharge plasma in the magnetic neutral line. Ion etching equipment.