JPH07273090A - Method and apparatus for surface treatment - Google Patents

Abstract

PURPOSE:To facilitate a high speed and high precision surface treatment with a simple apparatus construction by a method wherein an ion beam drawn out from a plasma is converted into a neutral beam and mixed with an ion beam and applied to an object to be treated. CONSTITUTION:An ion beam which is drawn out from an ion source 1 generating a plasma by ion drawing electrodes 4a, 4b and 4c is converted into a neutral beam in a charge exchange chamber 2. The neutral beam generated in the charge exchange chamber 2 is made to enter a treatment chamber 3 for the surface treatment of an object S to be treated. For this purpose, three mesh type ion repulsive electrodes 5a, 5b and 5c are provided between the charge exchange chamber 2 and the treatment chamber 3 and proper potentials are applied to the respective electrodes 5a, 5b and 5c to convert the ion beam drawn into the charge exchange chamber 2 into the neutral beam and make the neutral beam enter the treatment chamber 3. When the neutral beam is applied to the object S to be treated, a suitable level of an ion beam is mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method and apparatus, and more particularly, to supplying a neutral beam or a mixed beam of a neutral beam and an ion beam to a surface of an object to be treated, and performing etching or the like on the surface. The present invention relates to a surface treatment method and apparatus suitable for being applied to perform surface treatment.

[0002]

2. Description of the Related Art In surface treatment, for example, dry etching, conventionally, plasma is generated by high-frequency discharge or microwave discharge, and an object to be processed such as a semiconductor wafer is exposed to the plasma to etch the object to be processed. Was going on.

In this etching method, charged particles such as ions and electrons are incident on the object to be processed, so that an object to be processed, such as a gate oxide film or a resist film, is deposited as in the case of processing the gate of a transistor. When the body is processed, the object to be processed is charged up, the dielectric breakdown of the gate oxide film, the distortion of the transfer pattern of the resist film, and the so-called microloading effect in which the etching rate depends on the size of the resist pattern occur. . These phenomena become remarkable as the miniaturization of semiconductor elements progresses, and it is considered that they will become serious problems after the design rule of about 0.2 μm is adopted.

Since most of the above-mentioned phenomena are due to charged particles, in order to carry out etching processing with high accuracy and with little damage, neutral particles having no charge in a uniform direction, that is, a neutral beam. It has been considered desirable to use, and its technical development has been made. The use of the neutral beam for the surface treatment is effective not only in dry etching but also in film formation for forming an insulating film in terms of film quality and processing uniformity.

As a method of obtaining a neutral beam applied to the surface treatment such as dry etching and film formation as described above,
(1) Use of electron attachment, (2) Use of charge exchange reaction (Jpn. J. Appl. Phys., 29 (10), 22.
20 (1990)).

[0006]

As a method of obtaining the neutral beam (1), for example, there is a method of neutralizing the ion beam by an electron supply source (neutralizer) such as a filament (Japanese Patent Laid-Open No. Sho 62-62). -37382, JP-A-62-
174917), this method cannot obtain a sufficient beam flux because it has a small electron attachment probability and it is difficult to efficiently neutralize the ion beam.

As a technique for solving this drawback, there is a method of using a saddle field type high speed electron beam source. In this method, the neutralization efficiency can be 90% or more by properly setting the conditions. It is possible. However, this method has other drawbacks that the energy and the flux cannot be controlled independently, the energy of the obtained beam is relatively high, about 1 K eV or more, and the energy distribution width is wide (Vacuum, 38 (6), 469 (1988)
etc).

The method (2) for obtaining the neutral beam is as follows:
In order to obtain the highest possible neutral beam flux,
The device configuration is complicated because a device that generates an ion beam of a rare gas with a high probability of charge exchange reaction and a device that decomposes and supplies a halogen compound gas with high etching reactivity (hereinafter referred to as a halogen supply device) are combined. And there was a problem that it became expensive. Further, in this method, in order to ensure the uniformity of the treatment on the object to be treated, it is necessary to separate the halogen supply device to some extent from the object to be treated,
The length of the space in which the charge exchange reaction is performed (hereinafter referred to as the charge exchange chamber), that is, the transport distance of the ion beam becomes long,
As a result, the ion beam diverges, it is difficult to generate a high-density neutral particle beam, and the etching process cannot be performed at high speed.

As described above in detail, the surface treatment technique using only the neutral beam has an excellent advantage that etching and film formation can be performed with high accuracy, but the processing speed of etching is slow and There is a problem that the device used is complicated.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a surface treatment method and apparatus capable of performing high-speed and high-accuracy surface treatment with a simple apparatus configuration. And

[0011]

According to the present invention, when a surface treatment is performed by converting an ion beam extracted from plasma into a neutral beam and irradiating the surface of the object to be treated with the neutral beam,
The problem is solved by mixing the ion beam with the neutral beam with which the object to be processed is irradiated.

The present invention is also the above-mentioned surface treatment method, wherein the ion beam is mixed in an appropriate amount within a range not causing a problem in terms of surface treatment accuracy and reliability.

According to the present invention, in the above surface treatment method, the plasma is a mixed gas plasma using an inert gas and a reactive gas as raw materials.

According to the present invention, in the above surface treatment method, the reactive gas is a halogen compound.

According to the present invention, in the above surface treatment method, the halogen compounds are Cl F ₃ , NF ₃ and BBr ₃ .

Further, according to the present invention, an ion source for generating a plasma, a charge exchange chamber for converting an ion beam extracted from the plasma of the ion source by an ion extraction electrode into a neutral beam, and a charge exchange chamber for generating the ion beam are generated. In the surface treatment apparatus having a treatment chamber for treating the object to be treated by injecting the neutral beam, a part of the ion beam extracted into the charge exchange chamber is converted into the neutral beam and the neutral beam The above problem is similarly solved by providing a mixed beam generating means for causing a mixed beam of an ion beam to enter the processing chamber.

According to the present invention, in the above-mentioned surface treatment apparatus, the mixed beam generating means has a function of controlling the ratio of the ion beam contained in the mixed beam to 0 or more.

The present invention is also the above-mentioned surface treatment apparatus, wherein the mixed beam generating means is an ion repulsion electrode disposed between the charge exchange chamber and the treatment chamber.

According to the present invention, in the above surface treatment apparatus, the ion repulsion electrode is a plurality of mesh electrodes arranged so that the mesh positions are perpendicular to the advancing direction of the mixed beam and the mesh positions coincide with each other. It was done.

[0020]

As a result of various studies, the inventors of the present invention appropriately mix an ion beam, which causes a decrease in processing accuracy and reliability, with a neutral beam, without impairing reliability.
We have found that surface treatment such as etching can be performed with high precision and at high speed.

The present invention was made based on the above findings. In the present invention, when the ion beam extracted from the plasma is converted into a neutral beam and the surface of the object to be processed is treated with the neutral beam, Since the ion beam is mixed, for example, the amount of the ion beam mixed with the neutral beam can be arbitrarily controlled, and the ion beam can be mixed in an amount that does not cause a problem in terms of surface treatment accuracy and reliability. That is, by mixing in an amount such that the microloading effect due to the electric charge of the ions and the improper transfer of the pattern cannot be adversely affected and the etching rate can be increased, the reliability is not impaired. It becomes possible to perform surface treatment such as etching with high accuracy and high speed.

The amount of the ion beam mixed with the neutral beam may be several nA / cm ² or less. By mixing this amount of ion beam, there is no micro-loading effect, which is a characteristic of neutral beam etching, and the advantage of being able to transfer patterns accurately is utilized, while the slow etching rate, which was a problem in the past, is practical. You can improve up to speed.

In the present invention, the mixing amount of the ion beam within a range that does not cause a problem in terms of surface treatment accuracy and reliability is, for example, in the case of etching an insulating film formed on a wafer in the process of manufacturing a semiconductor element. In this case, since the etching shape abnormality caused by the ion beam depends on the film thickness, film type, pattern density, etc., it cannot be specified as a constant value.

Further, in the present invention, when the plasma is a mixed gas plasma using an inert gas and a reactive gas as raw materials, the mixed gas composed of the inert gas and the reactive gas may be turned into plasma. Therefore, the generation of ions that are the source of the ion beam and the halogen-containing radicals having high reactivity can be performed simultaneously in one plasma chamber, so that the device configuration can be greatly simplified.

At this time, by using a halogen compound having a relatively small number of constituent atoms such as Cl F ₃ , NF ₃ , and BBr ₃ as a reactive gas for generating radicals, the charge of the rare gas ion beam is increased. Even if it is present as a background gas during the exchange reaction, it does not interfere, and a rare gas neutral beam can be efficiently generated, and the processing speed can be improved. The reactive gas is not limited to these halogen compounds, but may be any other compound as long as it has reactivity corresponding to Cl F ₃ .

According to the present invention, in the surface treatment apparatus, a part of the ion beam extracted into the charge exchange chamber is converted into a neutral beam so that a mixed beam of the neutral beam and the ion beam is incident on the treatment chamber. Since the mixed beam generating means is provided, it is possible to reliably generate the mixed beam described above and perform the surface treatment of the object to be processed.

Further, in the present invention, when the mixed beam generating means is an ion repulsion electrode, a potential for repelling the ion beam in the mixed beam is applied to the ion repulsion electrode,
By adjusting the potential, the amount of ions passing through the ion repulsion electrode can be adjusted, so that the ion beam can be mixed and controlled at any desired ratio.

As such an ion repulsive electrode, an electrode composed of a plurality of mesh electrodes which are perpendicular to the advancing direction of the mixed beam and whose mesh positions coincide with each other in the advancing direction can be mentioned. In the conventional neutral beam etching apparatus, the ion repulsion electrode is arranged in order to completely remove the ions, but in the present invention, it is arranged for the purpose of controlling the amount of passing ions.

Generally, the energy of the ion beam is set by the potential applied to the plasma generation chamber. For example, in the etching apparatus shown in FIG.
To set the ion beam energy to, set the plasma chamber (ion source) itself to +400 V from ground,
The ion extraction electrode 4c has the same potential as the plasma chamber 1, the electrode 4b has about -500V, and the electrode 4a has 0V (earth potential).
Set to each. Also, the ion repulsion electrode 5c is 0-
The voltage is set to about 50V, and the electrode 5b is set to be smaller than + 400V when the ion beam is mixed in the substrate processing.
When the processing is performed only with the neutral beam, the voltage is higher than + 400V. Usually, the energy of the ion beam is determined by the total potential of the potential applied to the plasma chamber and the plasma potential, and since the ion beam itself has an energy width, the beam energy is 400 V applied to the plasma chamber. Somewhat higher than 400eV.
Therefore, in order to cut all the ion beams generated under the above conditions, for example, a potential of about +430 V is required. Further, 0V is set to the electrode 5a.

The feature of the present invention is to irradiate the object to be processed by making the potential applied to the ion repulsion electrode (electrode 5b in FIG. 1) smaller or larger than the beam extraction potential (potential applied to the plasma chamber). The purpose is to control the amount of ion beam mixed with the neutral beam.

[0031]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an etching apparatus (surface treatment apparatus) according to an embodiment of the present invention.

The etching apparatus of this embodiment is provided with an ion source 1 (ECR plasma ion source), a charge exchange chamber 2 and a processing chamber 3 as its basic configuration.

The above-mentioned ion source 1 which is a plasma generating chamber is provided with a microwave introduction window 1a and a gas introduction port 1b for introducing a raw material gas of plasma.
A coil 1c for generating a magnetic field inside the ion source 1.
1d is wound. Also, this coil 1c, 1d
Is covered with an iron shield 1e so that the magnetic field formed thereby contributes only to plasma generation.

The ion source 1 and the charge exchange chamber 2 are partitioned by three ion extraction electrodes 4a, 4b and 4c arranged in parallel, and the charge exchange chamber 2 and the processing chamber 3 are arranged in parallel. It is partitioned by the three ion repulsive electrodes 5a, 5b, 5c thus formed. The three ion repulsion electrodes are mesh electrodes in which a large number of meshes are formed, and each mesh electrode is arranged so as to be perpendicular to the advancing direction of the mixed beam and to have the mesh positions aligned in the same direction. .

The processing chamber 3 is provided with a sample holder 3a to which the object S to be processed is attached and whose temperature can be set constant. An exhaust device 6 is connected to the processing chamber 3, and a pressure control device (not shown) for the exhaust device 6 allows
The entire device can be set to a predetermined pressure.

Next, the operation of this embodiment will be specifically described by taking etching as an example.

First, in the sample holder 3a of the processing chamber 3,
A silicon wafer (object to be processed) S was installed, and the temperature of the silicon wafer S was set to 20 ° C. Polysilicon is formed on the surface of this silicon wafer S, and a mask of a line-and-space pattern of 0.3 to 1.0 μm is formed of photoresist on the polysilicon film.

Then, Ne gas (inert gas) was introduced at a rate of 15 sccm and Cl F ₃ gas was introduced at a rate of 4 sccm from the gas inlet 1b, and the pressure inside the apparatus was 2 × 10 ^-3 Torr.
The pressure control device (not shown) of the exhaust device 6 was adjusted so that Further, an ECR point (a point where the magnetic flux density is 875 gauss) is set inside the ion source 1 by supplying a current of 300 A to each of the coils 1c and 1d by a DC constant current power source (not shown). .

Under the above conditions, the oscillation frequency of 2.4
Waveguide 1 from a 5 GHz microwave power source (not shown)
Microwaves are introduced into the ion source 1 through f and the microwave introduction window 1a to generate ECR plasma inside the ion source, and in that state, the ion extraction electrodes 4a, 4b, and 4c generate about 400 eV of the ion source 1 An ion beam of energy was extracted and a part of the ion beam was converted into a neutral beam in the charge exchange chamber 2.

Generally, a minute time Δ is caused by the charge exchange reaction.
The amount ΔI of the ion beam that decreases per t can be expressed by the following equation.

The _{ΔI (t) = I A (} t) × U A (t) × N
_{B × σ ch (U A (} t)) × Δt Here, I _A is the ion beam current, U _A is the ion beam and the relative velocity of the target gas, the N _B density of the target gas, σ _ch (U _A (t )) Is the charge exchange cross section depending on the relative velocity U _A.

Now, suppose that the energy of the Ne ⁺ ion beam is 400 eV, the target gas is Ne, and the pressure is 2 mTo.
rr, and assuming that the length of the charge exchange zone is 15 cm, the conversion efficiency calculated using the above formula is about 30% (theoretical value). However, since there are Cl F ₃ gas and decomposition products such as Cl, Cl F, and F (decomposed in the ion source plasma) in addition to Ne in the charge exchange zone, Ne ⁺ ions and various Elasticity including charge exchange reaction between various gas particles,
It is considered that the ratio of Ne ⁺ ions converted into Ne is actually smaller than the theoretical value due to inelastic collision.

When the ion beam was converted into a neutral beam as described above, the ion repulsion electrodes 5a, 5
b, 5c, and only the beam that has a directionality within about 5.0 degrees from or perpendicular to the ion repulsion electrode 5a
It was possible to allow the light to enter the processing chamber 3 through 5b and 5c.

At that time, the ion beam remaining in the charge exchange chamber 2 without being converted into a neutral beam and the slow ions generated by the charge exchange pass through the ion repulsion electrodes 5c, 5b, 5a and enter the processing chamber 3. An appropriate electric potential was applied to the ion repulsion electrode to control the incidence rate. The amount of the ion beam in the mixed beam composed of the ion beam and the neutral beam is changed mainly by changing the value of the positive potential applied to the electrode 5b, and the ion repulsion electrode facing the processing chamber 3 is also changed. It is appropriate to apply a negative potential from 0 to 5a so that the electrons contained in the beam and the secondary electrons generated from the ion repulsion electrodes 5c and 5b do not reach the object.

Specifically, the ion extraction electrode has 4
a = 0V, 4b = -500V, 4c = 400V are set, and 5a = 0V, 5b = + 390 is set to the ion repulsion electrode.
By setting V, 5c = -10V, 2n A / cm
A mixed beam including about ² ion beams was made to enter the processing chamber 3. In the case of processing with only a neutral beam as in the conventional case, 5a = 0 on the ion repulsion electrode.
V, 5b = + 430V and 5c = -10V are set.

Actually, under the above conditions, when the polysilicon on the silicon wafer S installed on the holder 3a was etched by the mixed beam, an abnormal shape was obtained regardless of the density of the mask pattern. It was possible to achieve anisotropic etching. At this time, the etching rate of polysilicon is 810 Å / min, and the selection ratio to the resist is 3.
1, and the selection ratio to the silicon oxide film was 68.2.

Since the process conditions of the present embodiment described above are not optimized conditions, the above various characteristic values can be further improved.

Further, a 0.5 μm rule MOS capacitor was formed on a silicon wafer by the same etching method, and the electrical characteristics of the silicon oxide film were evaluated.
No deterioration of film quality was observed.

FIG. 2 shows the etching rate dependence and the etching rate when the potential applied to the ion repulsion electrode (mainly 5b) is changed under the above etching conditions to increase or decrease the ion beam amount in the mixed beam. The ratio is shown. This etching rate ratio is defined as (etching rate in line and space pattern) / (etching rate in open space portion without pattern). If this value is less than 1, the etching rate in the pattern is It is smaller than the open space part.

As is clear from FIG. 2, when the amount of ion beam in the mixed beam is increased, the etching rate is increased, but the etching rate ratio is above a certain level (about 6 nA / cm ^{2 in} this embodiment). It was found that as the amount was increased, it became smaller, resulting in non-uniform etching depending on the pattern size. This means that the ion beam flux incident on the silicon wafer S increases and the micro-rolling effect (etching rate dependence of pattern density) appears. However, no matter what the ion beam amount was from 0 to 16 nA / cm ² in the figure, there was no great difference in the electrical characteristics of the silicon oxide film of the MOS capacitor. It is considered that this is because the charged particle (ion beam) flux was about 2 to 3 orders of magnitude smaller than that in the case of plasma etching.

According to this embodiment described in detail above, the optimum range for mixing the ion beams (about 6 nA / cm ^{2 in} this embodiment) is used.
However, it has been clarified that the etching rate can be significantly improved as compared with the case of using the neutral beam alone, with high etching accuracy and reliability.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, in the above embodiment, the source gas is Ne.
Not limited to mixed gas of Cl and Cl F ₃ , other inert gas or NF
A mixed gas with other reactive gas such as ₃ , BBr ₃ or the like, a mixed gas with Ar gas and F ₂ gas, or the like may be used. NF ₃ ,
When a reactive gas such as BBr ₃ or F ₂ is used, the treatment can be basically performed under the same conditions as Cl F ₃ .

The surface treatment is not limited to etching but may be film formation, and the object to be treated is not limited to a silicon wafer coated with polysilicon.

Further, according to the device of the present invention, all the ions are removed by adjusting the potential of the ion repulsion electrode,
It is also possible to treat only with a neutral beam.

[0057]

As described above, according to the present invention,
With a simple device configuration, the object to be processed can be surface-treated at high speed without deterioration in film quality or abnormal etching shape due to electric charges.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an ion beam flux, an etching rate and an etching rate ratio for showing the effect of the embodiment.

[Explanation of symbols]

 1 ... Ion source 1a ... Microwave introduction window 1b ... Gas introduction port 1c, 1d ... Coil 1e ... Iron shield 1f ... Waveguide 2 ... Charge exchange chamber 3 ... Processing chamber 3a ... Sample holder 4a, 4b, 4c ... Ion extraction Electrodes 5a, 5b, 5c ... Ion repulsion electrode 6 ... Exhaust device S ... Silicon wafer

Claims (9)

[Claims] 1. When the ion beam extracted from the plasma is converted into a neutral beam and the surface of the object to be processed is irradiated with the neutral beam to perform surface treatment, the neutral beam irradiated to the object to be processed is ionized. A surface treatment method, which comprises mixing beams. 2. The surface treatment method according to claim 1, wherein the ion beam is mixed in an appropriate amount within a range not causing a problem in terms of accuracy and reliability of the surface treatment. 3. The surface treatment method according to claim 1, wherein the plasma is a mixed gas plasma using an inert gas and a reactive gas as raw materials. 4. The surface treatment method according to claim 3, wherein the reactive gas is a halogen compound. 5. The surface treatment method according to claim 4, wherein the halogen compound is Cl F ₃ , NF ₃ , or BBr ₃ . 6. An ion source for generating plasma, a charge exchange chamber for converting an ion beam extracted from the plasma of the ion source by an ion extraction electrode into a neutral beam, and a neutral beam generated in the charge exchange chamber. In a surface treatment apparatus having a treatment chamber for injecting a beam to treat an object to be processed, a part of the ion beam extracted into the charge exchange chamber is converted into a neutral beam, and the neutral beam and the ion beam are formed. A surface treatment apparatus comprising a mixed beam generation means for causing the mixed beam to enter a processing chamber. 7. The surface treatment apparatus according to claim 6, wherein the mixed beam generating means has a function of controlling the ratio of the ion beam contained in the mixed beam to 0 or more. 8. The surface treatment apparatus according to claim 6, wherein the mixed beam generating means is an ion repulsion electrode disposed between the charge exchange chamber and the processing chamber. 9. The ion repulsion electrode according to claim 8, wherein the ion repulsion electrode is a plurality of mesh electrodes arranged so as to be perpendicular to the advancing direction of the mixed beam and the mesh positions substantially coincide with each other in the advancing direction. And surface treatment equipment.