JP2956487B2 - Plasma generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generating apparatus, and more particularly, to a plasma generating apparatus for performing an etching process or a CVD process on a sample such as a semiconductor device substrate using plasma.

[0002]

2. Description of the Related Art A high-frequency electric power is introduced into a vacuum vessel under reduced pressure and low gas pressure to generate gas discharge to generate plasma, and the plasma is irradiated on the surface of a sample substrate to generate the sample. A plasma generation device that performs a process such as etching or thin film formation on a substrate (hereinafter, referred to as a plasma process) is indispensable for manufacturing a highly integrated semiconductor device and the like, and further develops a high performance plasma generation device. Research is progressing. In particular, there is a need for a plasma generation apparatus that does not damage semiconductor elements to be processed. Therefore, a plasma generation apparatus that can independently control the generation of plasma and the acceleration of ions in the generated plasma requires a dry etching technology. It is becoming an indispensable device for embedding technology in forming thin films.

FIG. 5 is a perspective view schematically showing an example of a plasma generating apparatus capable of performing a plasma processing without damaging a semiconductor element or the like to be processed, and FIG. 6 is a schematic view thereof. It is sectional drawing. The plasma generating apparatus shown in FIGS. 5 and 6 is disclosed in US Pat. No. 4,948,458 (registered in August 1990). In the figures, reference numeral 12 denotes a reaction vessel.

A high-frequency introduction window 14 is formed in the center of an upper wall 16 of the reaction vessel 12, and a dielectric plate 18 is adhered to the entire inside of the upper wall 16 as a window member. Sealed. A gas dispersion ring 52 is disposed directly below the dielectric plate 18, and the discharge gas introduced from the gas introduction passage 50 formed on the side surface of the reaction vessel 12 is once inside the gas dispersion ring 52. After entering, it is blown out from the nozzle 56 and uniformly dispersed inside the reaction vessel 12. Further, a gas exhaust path 51 is formed at a lower portion of the reaction vessel 12 so that the inside of the reaction vessel 12 can be maintained at a constant pressure by adjusting an exhaust speed by a vacuum pump. Further, a sample stage 13 is provided below the reaction vessel 12, and a sample substrate W is mounted on the sample stage 13.

On the other hand, on the dielectric plate 18 inside the high frequency introducing window 14, a coil 20 formed by spirally winding a band-shaped conductor is provided, and a central terminal 22 at the center and an outer terminal 22 are provided. Parts of the external terminals 24 are different from each other
7, 38. The strip-shaped conductor 38 connected to the external terminal 24 has a loop shape, and is connected to another strip-shaped conductor 37 via a capacitor 44. The loop-shaped band-shaped conductor 38 serves as a secondary coil, and a disk 40 around which a linear primary coil 36 is wound is disposed inside the band-shaped conductor 38. The primary coil 36 and the band-shaped conductor 38 Form a matching circuit. The primary coil 36 is a coaxial cable 3
2 is connected to a high frequency power supply (not shown).

[0006] In order to operate the plasma generating apparatus configured as described above, first, a discharge gas is introduced into the reaction vessel 12 through the gas introduction path 50 and the gas dispersion ring 52.
9 At this time, the exhaust system is also operated to keep the inside 19 of the reaction vessel 12 at a constant vacuum pressure. Next, when a high frequency of a predetermined frequency from the high frequency power supply is output through the coaxial cable 32, the coil 20 is output through the matching circuit.
The high frequency is applied to the dielectric plate 18 efficiently.
A magnetic field is induced in the interior 19 of the reaction vessel 12 through the reactor.
The induced magnetic field is the vector sum of the magnetic field from the spiral coil 20 and the magnetic field generated by the electron current in the plasma. As a result, a substantially uniform magnetic field is formed over the entire radial direction of the coil 20. , A uniform plasma is generated. Dielectric plate 18 and sample stage 1
3 is arranged in parallel with the coil 20 arranged thereon, and the coil 20 becomes parallel to the sample substrate W, so that the generated plasma becomes a planar plasma parallel to the sample substrate W.

When a high frequency is applied to the coil 20, a plane plasma parallel to the sample substrate W is formed as described above because the coil 20 in the reaction vessel 12 is formed.
In the flat plate region parallel to, the electrons move circularly due to the E × B drift, causing a uniform flow of electrons. Due to the circular movement of such electrons in the flat plate region, the electrons are generated by collision of electrons with individual gas molecules. This is because a uniform flow of ions and / or radicals in the generated plasma occurs. Further, since the sample substrate W is arranged in parallel with the coil 20, the plasma has very low energy in the direction of the sample substrate W. For this reason, damage to the sample substrate W by the plasma is extremely small.

FIG. 7 is a conceptual diagram schematically showing an example of a planar plasma generating apparatus in which the generation of plasma and the acceleration of ions in the invention can be controlled independently.

As shown in FIG. 7, by applying a high frequency between the coil 20 and the sample stage 13, the sample substrate W
Can control the energy of ions incident on the substrate. The sample stage 13 has a mechanism for adsorbing the sample substrate W such as an electrostatic chuck (not shown), and also has a heater or a cooling means, so that the temperature of the sample substrate W can be controlled.

When the plasma generating apparatus is operated, a discharge gas is introduced into the interior 19 of the reaction vessel 12 and a predetermined degree of vacuum is applied to the coil, as in the case of the plasma generating apparatus shown in FIGS. A high frequency is applied to 20 to generate plasma. At this time, in the plasma generating apparatus of FIG. 7, in order to control the anisotropy and acceleration energy of ions in the plasma, high-frequency power is applied to the sample table 13 on which the sample substrate W to be processed is placed, and the sample substrate W A bias voltage is generated on the surface. The bias voltage allows ions to be perpendicularly incident on the sample substrate W, controls the energy of the ions incident on the sample substrate W, and optimizes the conditions.

[0011]

As described above,
According to the above-described conventional plasma generating apparatus, the reaction vessel 1
It is described that uniform plasma parallel to the sample substrate W can be generated in the inside 19 of the sample 2 and damage to the sample substrate W can be extremely reduced.
Further, the sample stage 13 and the coil 20 of the plasma generating apparatus are used.
It is described that the energy of ions incident on the sample substrate W can be controlled if a device for applying a high frequency is connected between the sample and the substrate.

However, as a result of examining the plasma generation process in the above-mentioned conventional plasma generation apparatus, as shown in FIG. 5, a coil 20 wound in a simple spiral shape is used in the above-mentioned conventional plasma generation apparatus. Because
It has been found that the following problems exist.

FIG. 8A is a conceptual diagram showing the direction of the current flowing through the coil 20 at a certain moment, and FIG.
FIG. 3 is a cross-sectional view showing the direction of current and magnetic lines of force of each conductor of the coil 20. In the symbols shown in FIG. 8B, those in which a cross is indicated in a circle indicate that a current is flowing from the upper side to the lower side of the paper. The symbol "." In the figure indicates that the current is flowing from the bottom to the top of the page.

As shown in FIG. 8 (a), the current of the coil 20 flows in a uniform direction in the direction of rotation. At this time, the magnetic field induced by the current flow causes the current shown in FIG. 8 (b). As described above, a fixed line of magnetic force is formed extending from the top to the bottom at the center of the coil 20 and extending radially to the peripheral portion below the coil 20. Although not shown, the current flow in each conductor of the coil 20 may be completely reversed, in which case the direction of the magnetic field lines is completely reversed. Further, since the magnitude of the high-frequency current flowing through the coil 20 changes every moment, the magnitude of the magnetic field also changes, but the path itself in which the lines of magnetic force are formed hardly changes.

Therefore, the central portion of the coil 20 becomes a divergent source (or terminal port) of the magnetic field lines, and the portion immediately below the center of the coil 20 becomes a singular point. As a result, the density of the plasma generated by the application of the high-frequency power is significantly different from that of the surroundings at a position directly below the center of the coil 20, and the sample substrate W
When the etching process is performed on the coil 20, there is a problem that the etching rate is largely different in the vicinity of a position directly below the center of the coil 20.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and prevents the generation of plasma having a density different from that of the vicinity near the lower portion of the center of the coil, and achieves a uniform density in the entire lower radial region of the coil. It is an object of the present invention to provide a plasma generation apparatus capable of generating the above plasma.

[0017]

To achieve the above object, a plasma generating apparatus according to the present invention comprises: a metal reaction vessel having at least one window made of a dielectric plate;
In a plasma generation apparatus including a coil disposed outside the reaction container in close proximity to the window, and a circuit to which a high-frequency power supply that supplies high-frequency power to the coil is connected, the coil includes the coil, A first portion formed by winding a conductor in a spiral shape from the outside toward the center in a plane substantially parallel to the dielectric plate, and a first portion turned around in the opposite direction near the center of the first portion; And a second portion formed by winding the conductor in a spiral shape outwardly passing between the conductors of the first portion (1).

Further, the plasma generating apparatus according to the present invention is characterized in that, in the plasma generating apparatus according to the above (1), a circuit in which a high-frequency power source is connected between the coil and a sample stage inside the reaction vessel is provided. (2).

In the plasma generator according to the above (1) or (2), each of the conductors constituting the coil may have a circular or rectangular cross section. Therefore, the coil is formed using a conductor having a circular cross section. Alternatively, the coil may be formed using a strip-shaped conductive plate having a rectangular cross section. In the coil having the above-mentioned winding shape, first, a long conductor is bent at an appropriate curvature by 180 degrees to form a folded portion, and conductors continuous in parallel with each other on both sides of the folded portion are connected to the folded portion. Can be formed by spirally winding around the center. The conductor forming the coil needs to be a material having electric conductivity. Among them, it is preferable to use a conductor made of copper (Cu) from the viewpoint of high electric conductivity and low power loss in a high frequency region. .

The configuration of the portion other than the coil of the plasma generating apparatus described in the above (1) or (2) can be substantially the same as that of the above-described conventional plasma generating apparatus.

[0021]

FIG. 1A is a conceptual diagram showing a shape of a coil and a current flow used in the plasma generating apparatus according to the above (1) or (2) according to the present invention.
FIG. 2B is a cross-sectional view showing the direction of the current in the conductor constituting the coil and the direction of the lines of magnetic force generated thereby.

As is apparent from FIG. 1, the coil 11a according to the present invention has a first portion formed by winding a conductor in a spiral shape from the outside toward the center, and a coil near the center of the first portion. And a second portion formed by winding the conductor in a spiral shape outwardly passing between the conductors of the first portion and turning back between the conductors of the first portion. , A current always flows in opposite directions in the conductor of the first portion and the conductor of the second portion adjacent to each other. Therefore, as shown in FIG. 1 (b), at a certain moment, magnetic flux lines directed downward are formed between adjacent conductors in the center portion of the coil 11a, and magnetic flux lines directed upward are formed between adjacent conductors. Is formed, and thus the coil 11
In the entirety of a, magnetic lines of force upward and lines of magnetic force downward are formed alternately. On the other hand, on the lower side of the coil 11a, the magnetic lines of force in a certain direction are not formed, and on the lower side of each conductor, the magnetic lines of force toward the center of the coil 11a and the magnetic lines toward the periphery are formed alternately. When a current flows in a direction opposite to that in the case shown in FIG. 1, a magnetic field line in a direction completely opposite to the direction of the magnetic field lines shown in FIG. 1B is formed.

Therefore, a singular point does not occur in the vicinity of the lower part of the center of the coil 20 as in the case of the above-mentioned conventional plasma generating apparatus, and the lower part of the coil 11a has a planar plasma having a uniform density over the entire area in the radial direction. Are formed, and as a result, the sample substrate W can be uniformly etched.

Further, according to the plasma generating apparatus described in the above (2), since a circuit in which a high-frequency power source is connected between the coil and the sample stage inside the reaction vessel is provided, the circuit is described in the above (1). In addition to the operation described above, the energy of the ions incident on the sample substrate W is controlled by the high frequency applied to the sample stage.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma generating apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view schematically showing a plasma generating apparatus according to the embodiment.

The plasma generating apparatus shown in this figure is shown in FIGS. 5 and 6 except that the shape of the reaction vessel 15 is cylindrical and the coil 11a having the above-mentioned winding shape is used. Since the configuration is the same as that of the conventional plasma generation apparatus, detailed description other than members related to the coil 11a is omitted here.

As shown in FIG. 2, the coil 11a is disposed close to and parallel to the dielectric plate 18 inside the high frequency introduction window 14, and has a radially outer winding start end. And two external terminals 23 at the winding end. Although not shown in FIG. 2, these two external terminals 23 are connected to a high-frequency power applying means 25 having a matching circuit, a high-frequency power supply, and the like, similarly to the conventional plasma generating apparatus shown in FIGS. As a result, high-frequency power can be efficiently applied to the coil 11a.

In order to operate the above-described plasma generating apparatus, first, a discharge gas is supplied to the reaction vessel 15.
And the inside 19 of the reaction vessel 15 is maintained at a constant vacuum pressure. Next, when high-frequency power is applied to the coil 11a from the high-frequency power supply via the matching circuit, plasma having a uniform density over the entire radial direction of the coil 11a is formed in the inside 19 of the reaction vessel 15 below the coil 11a. Generated. At this time, unlike the plasma generator shown in FIG. 6, the plasma density in the vicinity of the lower portion at the center of the coil 20 does not become uneven. Dielectric plate 18 and sample stage 1
3, the coil 11a disposed on the dielectric plate 18 is substantially parallel to the sample substrate W, so that the generated plasma is substantially parallel to the sample substrate W and has a uniform plane. Plasma.

FIG. 3 is a conceptual diagram schematically showing another embodiment of the plasma generating apparatus according to the present invention. The plasma generating apparatus according to the present embodiment includes a high-frequency power applying unit 2 for applying high-frequency power between the coil 11a and the sample stage 13.
6 are provided. Further, the sample stage 13 has a mechanism for attracting the sample substrate W such as an electrostatic chuck (not shown), and a heater or a cooling means (not shown) is also provided, so that the temperature of the sample substrate W can be controlled. . Other members are configured in the same manner as in the plasma generating apparatus according to the above-described embodiment.

Next, the result of etching silicon (Si film) using the plasma generating apparatus shown in FIG. 3 will be described.

First, a sample substrate W having a photoresist pattern formed on an 8-inch silicon wafer is used, and chlorine (Cl ₂ ) is used as a discharge gas at 50.
The flow was at a flow rate of sccm, and the gas pressure was maintained at 10 mTorr. Next, the coil 11 having the above-described winding shape
a, a 13.56 MHz high-frequency power is supplied at a power of 1 kW to generate plasma.
a, a high frequency power of 800 kHz is supplied at a power of 50 W between the a and the sample stage 13 to control the energy of the ions incident on the sample substrate W, and the etching is performed for about 1 minute. 7 locations), the etching rate of the Si film was measured. FIG. 4 is a graph showing the result, in which the vertical axis indicates the etching rate of silicon and the horizontal axis indicates the in-plane position of the silicon wafer.

As a comparative example, an etching process was performed on a silicon wafer under the same conditions as in the above embodiment using the conventional plasma generation apparatus shown in FIG. The silicon etching rate at each position was measured. The result is also shown in FIG.

As is clear from the results shown in FIG. 4, when the plasma generating apparatus according to the embodiment is used, the etching proceeds at a substantially uniform speed over the entire surface of the silicon wafer, and the uniformity is ± It was within 5%. From the above results, in the plasma generating apparatus according to the embodiment shown in FIG. 3, the plasma having the uniform density is generated in the entire area in the radial direction below the coil 11 a in the inside 19 of the reaction vessel 15. It has been demonstrated that the entire surface of the silicon wafer can be etched at a uniform rate.

On the other hand, when the plasma generating apparatus shown as the comparative example was used, the etching rate became extremely high at the center of the silicon wafer, and the etching uniformity was poor.

In the above embodiment, the case where the plasma generating apparatus according to the present invention is used as an etching apparatus has been described. However, the application of the plasma generating apparatus according to the present invention is not limited to etching. Needless to say, it can be used for various applications such as a forming apparatus.

[0037]

As described in detail above, in the plasma generating apparatus (1) according to the present invention, a metal reaction vessel having at least one window made of a dielectric plate, and the reaction vessel In a plasma generating apparatus including a coil disposed close to the external window and a circuit to which a high-frequency power supply for supplying high-frequency power to the coil is connected, the coil has the above-described winding shape. Therefore, a singular point does not occur in the vicinity of the lower part of the center of the coil as in the case of the conventional plasma generating apparatus, and a uniform planar plasma can be formed over the entire area in the radial direction at the lower part of the coil. It becomes possible to uniformly etch the sample substrate over the entire surface. Further, the generated plasma has very low energy in the direction of the sample substrate, so that damage to the sample substrate can be extremely reduced.

[0038] In the plasma generating apparatus (2) according to the present invention, in the plasma generating apparatus according to the above (1), a high-frequency power source is connected between the coil and a sample table inside the reaction vessel. Since the circuit includes the above-described circuit, in addition to the effects achieved by the plasma generating apparatus described in (1) above,
The present invention has excellent effects, for example, the energy of ions incident on the sample substrate can be controlled, and the present invention can be applied to an embedding technique in forming a thin film on the sample substrate.

[Brief description of the drawings]

FIG. 1A is a conceptual diagram showing a shape of a coil and a current flow used in a plasma generating apparatus according to the present invention, and FIG. 1B is a diagram showing a direction of a current in a conductor constituting the coil, and FIG. It is sectional drawing which showed the direction of the magnetic force line produced | generated by this.

FIG. 2 is a perspective view schematically showing a plasma generation device according to an example.

FIG. 3 is a conceptual diagram schematically showing a plasma generation apparatus according to another embodiment.

FIG. 4 is a graph showing a relationship between an etching rate and an in-plane position of a wafer when etching a Si film using the plasma generating apparatuses according to the example and the comparative example.

FIG. 5 is a perspective view schematically showing a conventional plasma generation device.

FIG. 6 is a cross-sectional view schematically showing a conventional plasma generation device.

FIG. 7 is a conceptual diagram schematically showing another conventional plasma generating apparatus.

FIG. 8A is a conceptual diagram showing a shape of a coil and a current flow used in a conventional plasma generating apparatus, and FIG. 8B is a diagram showing a direction of a current in a conductor constituting the coil and a direction of the current. It is sectional drawing which showed the direction of the generated magnetic force line.

[Explanation of symbols]

 11a coil 15 reaction vessel 14 window for introducing high frequency

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/302 C

Claims (2)

(57) [Claims] 1. A metal reaction vessel having at least one window made of a dielectric plate, a coil disposed outside the reaction vessel close to the window, and a high-frequency And a circuit to which a high-frequency power supply for supplying power is connected, wherein the coil has a conductor formed in a spiral shape from the outside toward the center in a plane substantially parallel to the dielectric plate. A first portion formed by winding and a second portion formed by winding the conductor in a spiral shape outwardly passing between the conductors of the first portion and turning back in the vicinity of the center of the first portion. And a plasma generation device. 2. The plasma generating apparatus according to claim 1, further comprising a circuit connected to a high-frequency power supply between the coil and a sample stage inside the reaction vessel.