JP4122467B2 - High frequency discharge device and high frequency processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency discharge apparatus and a high-frequency processing apparatus used for manufacturing a thin film element on a semiconductor wafer or a plasma source such as a particle beam source, an analysis apparatus, or a heating apparatus.
[0002]
[Prior art]
An element (hereinafter referred to as a thin film element) on which a thin film including metal, metalloid, semiconductor, oxide, nitride, arsenic, or the like is formed is a memory device such as an LSI, a magnetic recording device, or an optical recording device, It is applied to the main parts of various devices such as semiconductor lasers, communication devices such as photoelectric conversion elements, flat displays such as LCDs, display devices such as solid-state image sensors, and energy devices such as solar cells. Technological development is expected as an indispensable part for advancing miniaturization and high performance.
[0003]
Such a thin film element has been refined in structure and improved in performance, and a manufacturing process using plasma, for example, in etching, CVD or the like is becoming important. And the area of the substrate of the object used in the manufacturing process is also increased from the viewpoint of improving productivity.
[0004]
In order to realize such a manufacturing process, an inductively coupled high-frequency plasma apparatus has attracted attention. This inductively coupled high-frequency plasma apparatus usually has a loop-shaped antenna arranged outside a vacuum vessel, and generates a plasma by applying an induction electric field to the gas in the vacuum vessel by flowing a high-frequency current through the antenna. It has become.
[0005]
In this case, the induction electric field generated by the antenna is applied to the gas in the vacuum container through a dielectric window installed in the vacuum container.
With such an inductively coupled high-frequency plasma, an induction electric field is generated in the vicinity of the antenna, and an electrostatic field due to the high-frequency voltage supplied to the antenna is also generated.
[0006]
The electrostatic coupling between the antenna and the plasma by the electrostatic field contributes to the start of plasma discharge and plasma generation in a low density region. As a result, this electrostatic coupling plays an important role in stabilizing the plasma discharge.
[0007]
[Problems to be solved by the invention]
However, as a result of electrostatic coupling between the antenna and the plasma, a negative DC self-bias voltage is generated in the antenna or the dielectric near the antenna, and ions generated by the discharge are accelerated by this self-bias voltage, Dielectric and antenna materials are sputtered. For example, if the material of the antenna is copper, the copper itself or ionized copper is sputtered onto the inner wall of the vacuum vessel or the object to be processed.
[0008]
This not only accelerates the deterioration of the high-frequency plasma apparatus, but sputtered impurities adversely affect processes such as etching and CVD.
Accordingly, an object of the present invention is to provide a high-frequency discharge device that can optimally control the electrostatic coupling between an antenna and plasma in order to achieve both stabilization of plasma discharge and suppression of sputtering by the antenna.
[0009]
Another object of the present invention is to provide a high-frequency processing apparatus capable of generating plasma in a state where the electrostatic coupling between the antenna and the plasma is optimally controlled and processing a target object.
[0010]
[Means for Solving the Problems]
According to claim 1, in a high-frequency discharge apparatus for generating plasma by generating an induced electric field in the vessel by supplying high frequency power to the small of Kutomo one loop-shaped antenna, the ground side of a single antenna or A capacitor is provided between each of the plurality of antennas . The capacitor is a variable capacitor. The capacitor is changed to change the high-frequency voltage distribution on the antenna, thereby electrostatically coupling the antenna and the plasma. The capacitance C of the capacitor is controlled so that the frequency of the high frequency is ω and the inductance in the circuit is L, C = 2 / ω ² This is a high-frequency discharge device that satisfies the relationship of L.
According to claim 2, in the high-frequency discharge device according to claim 1, the antenna is provided with or without an insulating coating on the outer peripheral side.
[0011]
According to the third aspect of the present invention, a vacuum vessel in which a plasma generating gas is supplied and an object to be processed is disposed, a power source for high frequency power, and induction of the high frequency power from the power source into the vacuum vessel. At least one loop-shaped antenna that generates an electric field to generate plasma and perform processing on an object to be processed in a vacuum vessel, and is interposed between the ground side of one antenna or a plurality of antennas, respectively. The capacitor is a variable capacitor, and the capacitance is changed to change the high-frequency voltage distribution on the antenna to control the electrostatic coupling between the antenna and the plasma. If the high frequency is ω and the inductance component in the circuit is L, C = 2 / ω ² This is a high-frequency processing apparatus that satisfies the relationship of L.
According to claim 4 , in the high-frequency processing apparatus according to claim 3 , the antenna is provided with or without an insulating coating on the outer peripheral side .
According to claim 5, in the high frequency processing apparatus according to claim 3, a plurality of antennas are provided inside the vacuum vessel.
According to claim 6, in the high-frequency processing apparatus according to claim 3, the antenna is provided outside the vacuum vessel.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(1) A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a high-frequency processing apparatus according to the present invention.
The vacuum vessel 1 is formed, for example, in a cylindrical shape, and a supply pipe 3 for supplying a process gas 2 such as a reactive gas for etching and a raw material gas for CVD is connected to the upper portion thereof as shown in FIG. In addition, an exhaust pipe 4 is connected to the lower part thereof. The vacuum container 1 is not limited to a cylindrical shape, and may be formed in a cubic shape.
[0018]
An exhaust pump 5 is connected to the exhaust pipe 4, and the inside of the vacuum vessel 1 is decompressed by the operation of the exhaust pump 5.
Further, a table 6 is provided in the vacuum vessel 1, and a workpiece 7 to be etched or CVD processed is placed on the table 6.
[0019]
Further, a loop-shaped antenna 8 is disposed in the vacuum vessel 1. The antenna 8 is made of, for example, a conductive material such as copper or aluminum.
[0020]
The antenna 8 is of two types: an antenna conductor whose outer periphery is coated with an insulating material, for example, glass fiber, or an antenna conductor that is not coated with metal.
[0021]
As shown in FIG. 1, a power source 9 for high frequency power is connected to one end of the antenna 8, and a floating capacitor 10 is connected to the ground on the other end side.
[0022]
The floating capacitor 10 has a variable capacitance, and has an action of controlling the electrostatic coupling between the antenna 8 and the plasma P by changing the capacitance C _f to change the high frequency voltage distribution on the antenna 8. Yes.
[0023]
That is, if the floating capacitor 10 is not connected to the antenna 8 as shown in FIG. 3 (a), the voltage at the point A with respect to the ground is 0V as shown in FIG. 3 (b). A voltage waveform corresponding to the voltage between A and B of the antenna 8 appears between them as shown in FIG. This waveform is the same for point B with respect to ground as shown in FIG.
[0024]
On the other hand, when the floating capacitor 10 is connected to the antenna 8 as shown in FIG. 4 (a), the point A and the point B as shown in FIG. A voltage waveform having a half-phase amplitude opposite to that of the voltage phase {FIG. 4 (c)} appears.
[0025]
Therefore, the voltage at the point B from the ground has a waveform in which the voltage of the opposite phase by the floating capacitor 10 shown in FIG. 5B and the voltage between the points A and B shown in FIG. The maximum voltage becomes smaller as shown in FIG.
[0026]
Therefore, by changing the capacitance C _f of the floating capacitor 10, the voltage distribution on the antenna 8 is changed to control the voltage at an arbitrary point on the antenna 8 (for example, the midpoint between the points A and B) to 0V. It will be possible.
[0027]
When the voltage at this intermediate point is 0 V, the circuit shown in FIG.
V = {(jωL / 2) + j (1 / ωC _f )} · I (1)
It becomes. Here, L is the inductance of the antenna 8, C _f is the capacitance of the floating capacitor, and I is the circuit current.
[0028]
In this case, the equation is modified to C _f = 2 / ω ² L (2)
It becomes.
[0029]
When this value is taken, the point B from the ground is halved compared to the case where there is no capacitor for high-frequency voltage, and electrostatic coupling can be greatly suppressed.
Here, in order to investigate the effect of the floating capacitor 10, the high-frequency voltages V _RF1 and V _RF2 at both ends of the antenna 8, the negative DC self-bias voltage V _{DC of the} antenna 8, and the electron density _ne were measured.
[0030]
5 and 6 self-bias voltage V _DC of the antenna 8 (in FIG absolute value | V _DC | Show), the ends of the antenna 8 RF voltage V _RF1, V _RF2, of the floating capacitor 10 for the electron density n _e The dependence of the capacitance C _f is shown.
[0031]
In this case, the antenna 8 was discharged with, for example, 0.3 Pa of argon using a solid stainless steel antenna.
As shown in FIG. 5, as the capacitance C _f of the floating capacitor 10 is decreased, the high-frequency voltage V _RF1 on the power source 9 side is decreased, the high-frequency voltage V _RF2 on the floating capacitor 10 side is increased, and the capacitance C _{f of the} capacitor 10 is increased. The magnitude reverses in the vicinity of 400 pF.
[0032]
Further, the self-bias voltage | V _DC | initially decreases as the capacitance C _{f of the} capacitor 10 is decreased, becomes minimum when V _RF1 = V _RF2, and then increases again.
[0033]
This indicates that the strength of electrostatic coupling can be controlled by changing the capacitance C _f of the floating capacitor 10.
In FIG. 6, the electron density _ne is maximized when the self-bias voltage | V _DC | is minimized. This indicates that when the electrostatic coupling between the antenna 8 and the plasma P is suppressed, the generation efficiency of the plasma P is increased.
[0034]
Meanwhile, in order 7 and 8 to examine the effects of the same floating capacitor 10, using the antenna 8 which is an insulating coating, the high-frequency voltage V _RF1 at both ends of the antenna 8, V _RF2, the electron density n _e It is the result of having measured each. The negative DC self-bias voltage V _DC of the antenna 8 cannot be measured because it appears on the surface of the insulator in the plasma P, not the antenna conductor.
[0035]
Even when this antenna 8 with insulation coating is used, the high-frequency voltages V _RF1 and V _RF2 at both ends of the antenna 8 are V _RF1 = V _{RF2 in the} vicinity where the capacitance C _f of the floating capacitor 10 is 400 pF, as described above. And has the same tendency that the electron density _ne is maximized.
[0036]
This indicates that the electrostatic coupling between the antenna 8 and the plasma P can be controlled by changing the capacitance C _f of the floating capacitor 10 even if the antenna 8 is provided with an insulating coating.
[0037]
Even when the antenna 8 is arranged outside the vacuum vessel 1, the antenna 8 and the plasma P are not changed from the case where the antenna 8 is arranged inside the vacuum vessel 1 in that the antenna 8 and the plasma P are coupled via a dielectric. Therefore, even when the antenna 8 is arranged outside the vacuum vessel 1, electrostatic coupling between the antenna 8 and the plasma P can be controlled by changing the capacitance C _f of the floating capacitor 10.
[0038]
In the processing by such a high-frequency processing apparatus, the induction electric field is reactive for etching in the vacuum vessel 1 by applying a high-frequency current from the power source 9 to the loop antenna 8 arranged inside the vacuum vessel 1. It is added to a process gas 2 such as a gas or a raw material gas for CVD, thereby generating plasma P, and processing such as etching or thin film formation is performed on the object 7 to be processed.
[0039]
Thus, in the first embodiment, the floating capacitor 10 is connected to the ground side of the antenna 8, and the capacitance C _f of the floating capacitor 10 is changed to change the high-frequency voltage distribution on the antenna 8, Since the electrostatic coupling between the antenna 8 and the plasma P is controlled, the electrostatic coupling between the antenna 8 and the plasma P in order to achieve both the stabilization of the plasma P discharge and the suppression of sputtering by the antenna 8. Can be optimally controlled.
[0040]
As a result, ions are accelerated by the negative DC self-bias voltage, and for example, it is possible to prevent the antenna material from being sputtered on the inner wall of the vacuum vessel 1 or the object 7 to be processed, thereby extending the life of the high-frequency plasma apparatus. This will not adversely affect processes such as etching and CVD.
(2) Next, a second embodiment of the present invention will be described. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0041]
FIG. 9 is a block diagram of the high frequency processing apparatus.
Inside the vacuum vessel 1, a plurality of loop antennas having different diameters, for example, two antennas 20, 21 are arranged.
[0042]
These antennas 20 and 21 are made of, for example, a conductive material such as copper or aluminum.
These antennas 20 and 21 are of two types, the antenna conductor having an outer periphery coated with an insulating material such as glass fiber, or the antenna conductor without metal coating.
[0043]
The antennas 20 and 21 are connected in series, and the floating capacitors 22 and 23 are connected between the antennas 20 and 21, respectively.
These floating capacitors 22 and 23 have variable capacitances, respectively, and change the high-frequency voltage distribution on the antennas 20 and 21 by changing their capacitances C _f , and the electrostatic capacitance between the antennas 20 and 21 and the plasma P is changed. It has the effect of controlling the mechanical coupling.
[0044]
That is, as in the first embodiment, by changing the capacitance C _f of each floating capacitor 22, 23, the voltage distribution at each antenna 20, 21 can be arbitrarily controlled, and any arbitrary antenna on the antenna can be controlled. The point can be set to 0 V, and the voltage from the ground to each of the antennas 20 and 21 can be reduced.
[0045]
In such a high-frequency processing apparatus, the induction electric field is etched in the vacuum vessel 1 by applying a high-frequency current from the power source 9 to the two loop antennas 20 and 21 arranged inside the vacuum vessel 1. Is added to a process gas 2 such as a reactive gas for CVD or a raw material gas for CVD, thereby generating a plasma P, and processing such as etching or thin film formation on the object 7 is performed.
[0046]
In the form of the thus the second embodiment, the on two floating capacitors 22 and 23 connect the two by changing the respective capacitance C _f antenna 20, 21 between each of the antennas 20, 21 Since the high frequency voltage distribution is changed and the electrostatic coupling between the antennas 20 and 21 and the plasma P is controlled, as in the first embodiment, the stabilization of the plasma P discharge and the antenna 20, Needless to say, it is possible to optimally control the electrostatic coupling between the antennas 20 and 21 and the plasma P in order to achieve both the suppression of sputtering by 21.
(3) Next, a third embodiment of the present invention will be described. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0047]
FIG. 10 is a block diagram of the high frequency processing apparatus.
A plurality of loop antennas, for example, three antennas 30, 31, and 32 are arranged on the outer periphery of the vacuum vessel 1.
[0048]
These antennas 30, 31, and 32 are made of, for example, a conductive material such as copper or aluminum.
Further, these antennas 30, 31, and 32 are made of a solid metal of an antenna conductor without applying an insulating coating.
[0049]
The antennas 30, 31, and 32 are connected in series, and floating capacitors 33, 34, and 35 are connected between the antennas 30, 31, and 32, respectively.
These floating capacitors 33, 34, and 35 are variable capacitors, respectively, and change the high-frequency voltage distribution on each antenna 30, 31, 32 by changing each capacitance C _f , and It has the effect of controlling electrostatic coupling with the plasma P. The antennas 30, 31, and 32 are wound around, for example, a quartz member 36 that forms a part of the vacuum vessel.
[0050]
That is, as in the first embodiment, by changing the capacitances C _f of the floating capacitors 33, 34, and 35, the voltage distribution in the antennas 30, 31, and 32 can be arbitrarily controlled to change the antennas. The upper arbitrary point can be set to 0 V, and the voltage from the ground to each antenna 30, 31, 32 can be reduced.
[0051]
In the processing by such a high-frequency processing apparatus, an induction electric field is generated in the vacuum vessel 1 by supplying a high-frequency current from the power source 9 to the two loop antennas 30, 31, 32 arranged inside the vacuum vessel 1. Is added to the process gas 2 such as a reactive gas for etching and a raw material gas for CVD, thereby generating a plasma P and performing processing such as etching or thin film formation on the object 7 to be processed.
[0052]
As described above, in the third embodiment, the floating capacitors 33, 34, and 35 are connected between the three antennas 30, 31, and 32, and the capacitances C _f are changed to change the three antennas 30, Since the high frequency voltage distribution on 31 and 32 is changed and the electrostatic coupling between the antennas 30, 31, 32 and the plasma P is controlled, the plasma P is the same as in the first embodiment. It goes without saying that the electrostatic coupling between the antennas 30, 31, 32 and the plasma P can be optimally controlled in order to achieve both stabilization of discharge and suppression of sputtering by the antennas 30, 31, 32.
[0053]
In the above description, a processing apparatus using high frequency is described. However, a high frequency discharge apparatus used for heating an object to be processed (for example, metal) in a normal pressure vessel such as a high frequency heating apparatus can be provided.
[0054]
【The invention's effect】
As described in detail above, according to the present invention , the high-frequency voltage distribution on the antenna is changed by changing the capacitance of the capacitor interposed between the antenna ground side or between the plurality of antennas. By controlling the electrostatic coupling, it is possible to provide a high-frequency discharge device capable of optimally controlling the electrostatic coupling between the antenna and the plasma in order to achieve both stabilization of plasma discharge and suppression of sputtering by the antenna.
[0055]
In addition, according to the present invention, the capacitance of the capacitor interposed between the antenna ground side or the plurality of antennas is changed to change the high-frequency voltage distribution on the antenna, thereby electrostatically coupling the antenna and the plasma. By controlling this, it is possible to provide a high-frequency processing apparatus capable of generating plasma in a state in which the electrostatic coupling between the antenna and the plasma is optimally controlled and processing the object to be processed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a high-frequency processing apparatus according to the present invention.
FIG. 2 is a configuration diagram inside a vacuum vessel in the apparatus.
FIG. 3 is a diagram for explaining a high-frequency voltage distribution on an antenna when there is no floating capacitor.
FIG. 4 is a diagram for explaining a high-frequency voltage distribution on an antenna when a floating capacitor is connected.
FIG. 5 is a graph showing the dependence of the capacitance of a floating capacitor on the self-bias voltage V of the antenna when a solid metal antenna is used.
FIG. 6 is a graph showing the dependence of the capacitance of the floating capacitor on the self-bias voltage of the antenna when a solid metal antenna is used.
FIG. 7 is a diagram showing the dependence of the capacitance of a floating capacitor on the self-bias voltage V of the antenna when an antenna with an insulation coating is used.
FIG. 8 is a diagram showing the dependence of the capacitance of the floating capacitor on the self-bias voltage V of the antenna when an antenna with an insulation coating is used.
FIG. 9 is a configuration diagram showing a second embodiment of the high-frequency processing device according to the present invention.
FIG. 10 is a configuration diagram showing a third embodiment of a high-frequency processing device according to the present invention.
[Explanation of symbols]
1: vacuum container,
2: Process gas,
7: Work piece
8, 20, 21, 30, 31, 32: Loop antenna,
9: Power supply for high frequency power,
10, 22, 23, 33, 34, 35: floating capacitors.

Claims (6)

In high-frequency discharge apparatus for generating plasma by generating an induced electric field in the vessel by supplying high frequency power to the small of Kutomo one loop-shaped antenna,
A capacitor interposed between the ground side of the one antenna or the plurality of antennas ,
The capacitor is a variable capacitance, and changes the high-frequency voltage distribution on the antenna by changing the capacitance, and controls the electrostatic coupling between the antenna and the plasma,
The capacitor C has a high frequency ω and an inductance L in the circuit.
C = 2 / ω ² Satisfy the relationship of L,
A high-frequency discharge device characterized by that.   The high-frequency discharge device according to claim 1, wherein the antenna has an outer peripheral side or an insulating coating. A vacuum vessel in which a gas for plasma generation is supplied and an object to be processed is disposed therein;
A power supply for high frequency power,
At least one loop-shaped antenna for generating plasma by generating an induction electric field in the vacuum vessel by supplying high-frequency power from the power source, and performing processing on the object to be processed in the vacuum vessel;
A capacitor interposed between a ground side of one of the antennas or a plurality of the antennas;
Comprising
The capacitor is a variable capacitance, and changes the high-frequency voltage distribution on the antenna by changing the capacitance, and controls the electrostatic coupling between the antenna and the plasma,
The capacitor C has a high frequency ω and an inductance component in the circuit L,
C = 2 / ω ² Satisfy the relationship of L,
A high frequency processing apparatus characterized by the above. 4. The high frequency processing apparatus according to claim 3 , wherein the antenna has an outer peripheral side or an insulating coating . The high-frequency processing apparatus according to claim 3 , wherein a plurality of the antennas are provided inside the vacuum vessel . The high-frequency processing apparatus according to claim 3 , wherein the antenna is provided outside the vacuum container .

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