JP2007048621A - Plasma treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment apparatus with a high treatment rate without damages of a sample surface by plasma. <P>SOLUTION: In this plasma treatment apparatus provided with an electrode unit provided with an applicator to which power generated from a power supply is applied and a counter electrode facing the applicator through an insulator, and an impedance component inserted between the counter electrode and ground potential, the electrode unit faces a sample with a gap, reactive gas is locally supplied to the space formed between the electrode unit and the sample, and plasma is generated between the applicator and the counter electrode with the power applied to the applicator to treat the sample using the reactive gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus that performs surface treatment using plasma.

  At present, a surface treatment apparatus using plasma is widely used as an apparatus for performing surface treatment such as etching, film formation, ashing, and surface hydrophilization in a multilayer structure of various devices such as semiconductors and liquid crystal display devices. Among them, in recent years, an atmospheric pressure plasma processing apparatus that generates plasma at a pressure near atmospheric pressure and processes a sample has been developed for the purpose of high-speed processing, cost reduction of the apparatus, reduction of the area occupied by the apparatus, and the like.

  As one of the above atmospheric pressure plasma processing apparatuses, an electrode unit having an electric power source and an application electrode to which electric power from the electric power source is applied and a ground electrode opposed to the application electrode through an insulator are collectively provided as the electrode unit. The unit is opposed to the sample, and a high-pressure reaction gas region including atmospheric pressure is formed between the electrode unit and the sample, and only the region close to the sample between the application electrode and the ground electrode is exposed to the reaction gas. There is known an apparatus for generating a high-pressure plasma based thereon and processing a sample with active species generated in the high-pressure plasma (see, for example, Patent Document 1).

Hereinafter, the high-pressure plasma apparatus described in Patent Document 1 will be described with reference to FIG.
FIG. 13 is a cross-sectional view of an electrode levitation type high-voltage levitation electrode, and is a schematic diagram illustrating a configuration of an apparatus described in Patent Document 1.
In FIG. 13, H1 is an electrode floating type high pressure floating electrode, 101 is a high pressure reaction gas supply port, 102 is a reaction gas exhaust port, 103 is an inner electrode, 104 is an outer electrode, 105 is an insulator, and 106 is an open end of a power transmission line 107 is a sample stage, 108 is a sample, 109 is high-pressure plasma, 110 is a reactive gas flow, and D is the distance between the electrode H1 and the sample 108.

  The electrode floating type high voltage floating electrode H1 is formed by the inner electrode 103, the outer electrode 104, and the insulator 105, and the electrode H1 and the sample 108 are arranged to face each other in a predetermined gas atmosphere. At this time, when a high-pressure reaction gas is supplied from the high-pressure reaction gas supply port 101, a reaction gas flow 110 is formed from the high-pressure reaction gas supply port 101 toward the reaction gas exhaust port 102 or the surrounding gas atmosphere, and the supplied high-pressure reaction is performed. Due to the differential pressure between the gas and the ambient gas atmosphere, the electrode H1 floats by a distance D. Since the distance D is narrow, the electrode H1 and the sample 108 are moved from the high-pressure reaction gas supply port 101 to the reaction gas exhaust port 102. The reaction gas flow path and the reaction gas flow path from the high pressure reaction gas supply port 101 to the gas atmosphere around the electrode H1 become a low conductance gas flow path, and a high pressure reaction gas region is formed in a portion sandwiched between the electrode H1 and the sample 108. To do. Here, the pressure in the high-pressure reaction gas region may be atmospheric pressure.

  At this time, the reaction from the high-pressure reaction gas supply port 101 to the reaction gas exhaust port 102 can be similarly performed by placing the electrode H1 so as not to float with respect to the sample 108 and disposing the electrode H1 and the sample 108 close to each other. The gas flow path and the reaction gas flow path from the high pressure reaction gas supply port 101 to the periphery of the electrode become a low conductance gas flow path, and a high pressure reaction gas region can be formed in a portion sandwiched between the electrode and the sample 108. .

  Further, the inner electrode 103 is connected to a power source (not shown), and at the same time, the outer electrode 104 is grounded, and a power transmission line is formed in an insulator 105 portion sandwiched between the inner electrode 103 and the outer electrode 104. The power generated from the power source is applied to the inner electrode 103, reaches the power transmission line open end 106 through the power transmission line formed between the inner electrode 103 and the outer electrode 104, and is formed between the electrode H 1 and the sample 108. In the high-pressure reaction gas region, a local high-pressure plasma 109 is generated at a position away from the high-pressure reaction gas supply port 101, and the film 108 is formed, processed, and surface-treated by the active species generated by the high-pressure plasma 109. Further, the entire sample 108 is processed by relatively moving the sample 108 and the electrode H1.

At this time, the apparatus does not generate plasma between the inner electrode 103 to which electric power is applied and the sample 108, but the high-pressure plasma 109 between the inner electrode 103 to which electric power is applied and the outer electrode 104 that is grounded. Since the active species generated in the plasma are diffused on the surface of the sample 108 to perform film formation, processing, and surface treatment, the sample 108 is not in direct contact with the plasma and the sample 108 is not damaged.
JP 2000-306848 A

Here, the inner electrode 103 and the outer electrode 104 are long electrodes having a longitudinal direction in a direction perpendicular to the paper surface, and are perpendicular to the paper surface at the power transmission line open end portion 106 where the inner electrode 103 and the outer electrode 104 face each other. Consider the case of generating a line-shaped atmospheric pressure plasma that is long in the direction.
FIG. 14 shows the electric field intensity distribution calculation result when a high frequency voltage having an amplitude of 1.0 [kV] and a frequency of 13.56 [MHz] is applied to the inner electrode 103 and the outer electrode 104 is grounded.

  The surface of the sample 108 is Y = 0 [mm], the center of the inner electrode 103 is X = 0 and Z = 0 [mm], and the distance between the substrate and the lower surface of the electrode unit H1 is D = 4.0 [mm]. Yes. The distance between the inner electrode 103 and the outer electrode 104 is 3.0 [mm], and the insulator 105 disposed between the inner electrode 103 and the outer electrode 104 is alumina (relative dielectric constant εr = 9.4). The calculation was performed assuming that the portion between the inner electrode 103 and the outer electrode 104 has a recess with a height of 3.0 mm and a base of 7.0 mm. The sample 108 is made of glass having a thickness of 5.0 mm and a dielectric constant of 5.5, and the lower side of the sample 108 is made of air.

  In addition, the electric field intensity distribution immediately below the inner electrode 103 (X = 0 [mm], Z = 0 [mm], region A) and the central portion (X = 5.5 [X] of the distance between the inner electrode 103 and the outer electrode 104). mm], Z = 0 [mm], region B), and the electric field intensity distribution immediately below the outer electrode 104 (X = 11.0 [mm], Z = 0 [mm], region C) is shown in FIG.

As shown in FIGS. 14 and 15, it can be seen that the largest electric field strength of 7.78E5 [V / m] is generated in the recessed portion of the insulator 105 between the inner electrode 103 and the outer electrode 104. At this time, 1.35E5 [V / m] is also applied to the vicinity of the sample surface immediately below the inner electrode 103.
An electric field strength of 0.3 [V / m] is generated in the vicinity of the sample surface immediately below the outer electrode 104.

  At this time, when the applied voltage to the inner electrode 103 is increased, atmospheric pressure plasma corresponding to the reaction gas is generated in the hollow portion of the insulator 105 between the inner electrode 103 and the outer electrode 104 where the greatest electric field strength is generated. The film is formed, processed, and surface-treated on the surface of the sample 106 by the active species generated in the atmospheric pressure plasma. In order to further increase the processing speed, the input power to the inner electrode 103, that is, the applied voltage is set. Increasing the pressure promotes the decomposition of the atmospheric pressure plasma generated between the inner electrode 103 and the outer electrode 104, and at the same time increases the electric field strength near the surface of the sample 108 immediately below the inner electrode 103. Atmospheric pressure plasma is also generated on the surface of the sample 108, and there is a problem that the sample surface is damaged by direct contact of the atmospheric pressure plasma with the sample surface. Conversely, power and voltage can be applied to the inner electrode 103 only to the extent that atmospheric pressure plasma is not generated on the surface of the sample 108, and the upper limit of input power is defined, and a high processing speed cannot be achieved. It has.

  At this time, from the calculation results of FIGS. 14 and 15, assuming that the highest electric field strength in the vicinity of the inner electrode 103 is Ep and the highest electric field strength on the surface of the sample 108 is Es, Ep / Es = 7.78E5 / 1 .35E5 = 5.8 times. This increases the applied voltage to the inner electrode 103, and the applied voltage is 5.8 times the applied voltage when atmospheric pressure plasma is generated in the portion of the highest electric field strength Ep between the inner electrode 103 and the outer electrode 104. When applied to the inner electrode 103, the portion of the highest electric field strength Es on the surface of the sample 108 also reaches the plasma generation electric field strength, indicating that atmospheric pressure plasma is generated on the sample surface and damages the surface of the sample 108. ing.

  According to the present invention, an electrode unit including an application electrode to which power generated from a power source is applied, a counter electrode facing the application electrode with an insulator interposed therebetween, and the counter electrode and the ground potential are inserted An impedance element is provided, the electrode unit is opposed to the sample with a gap, and a reactive gas is locally supplied to a space formed between the electrode unit and the sample, and the power applied to the applied electrode The present invention provides a plasma processing apparatus for generating a plasma between the application electrode and the counter electrode and processing a sample based on a reaction gas.

In the present invention, the applied electrode and the counter electrode have an impedance Zc therebetween, and the impedance Z of the impedance element is Z = Zc (A · Exp [jθ] −1), where θ is an arbitrary real number, A May be a real number satisfying 0 ≦ A <1 and 0.5 ≦ A · cos θ.
The application electrode and the counter electrode may have an impedance Zc between them, and the impedance Z of the impedance element may be Z = −Zc / 2.
Furthermore, the applied electrode and the counter electrode have an impedance Zc between them, and the impedance Z of the impedance element is Z = j · Im [Zc (A · Exp [jθ] −1)], where θ is an arbitrary real number , A may be a real number satisfying 0 ≦ A <1 and 0.5 ≦ A · cos θ.
The impedance element may be formed of a series circuit of an inductance element and a variable capacitance element.

  According to the present invention, a plasma having a higher processing speed is generated by generating a large electric field strength near the electrode without damaging the sample surface, and generating an atmospheric pressure plasma having a high decomposition rate and active species density. A processing device can be realized.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing a first embodiment of the present invention, FIG. 2 is an equivalent circuit diagram inside the electrode unit, FIG. 3 is a diagram showing a relationship 1 between Z and Zc, and FIG. 4 is a diagram showing a relationship 2 between Z and Zc. 5 is an explanatory diagram of the relationship 3 between Z and Zc.
6 and 7 are a calculation result of the electric field intensity distribution near the sample when the impedance Z is inserted, and an electric field intensity distribution calculation graph near the sample.
8 and 9 are a calculation result of the electric field intensity distribution near the sample when the impedance Z is not inserted, and an electric field intensity distribution calculation graph near the sample.
FIG. 10 is a graph showing changes in the voltage ratios Vc / V and Vz / V, and FIG.
It is a graph which shows the change of p1 / Es1.

  In FIG. 1, 1 is an applied electrode, 2 is a counter electrode, 3 is an insulator, 4 is a ground metal housing, 5 is an electrode unit, 6 is a power transmission line, 7 is an impedance circuit element Z, 8 is a power source, 9 is Matching box 10 is a sample, 11 is a reactive gas supply port, 12 is a reactive gas exhaust port, 13 is a reactive gas flow, and 14 is an atmospheric pressure plasma.

  The three application electrodes 1 and the four counter electrodes 2 are elongated electrodes extending in a direction perpendicular to the paper surface. The application electrode 1 and the counter electrode 2 are arranged to face each other with an insulator 3 interposed between them. 1, the counter electrode 2, the insulator 3, and the ground metal casing 4 form an electrode unit 5, and the electrode unit 5 and the sample 10 are arranged in a predetermined gas atmosphere. Further, the electrode unit 5 is arranged so as to be relatively movable with respect to the sample 10 so that the interval is G, and a desired reaction gas is supplied from the reaction gas supply port 11, and a reaction gas exhaust port is provided. When the gas is exhausted from 12, the reaction gas flow 13 flows through the reaction gas flow path formed between the sample 10 and the electrode unit 5.

The power supply 8 has a pair of output terminals, and the three application electrodes 1 are connected to one output terminal of the power supply 8 through the power transmission line 6 and the matching box 9, and the other output terminal of the power supply 8 is grounded. The four counter electrodes 2 are grounded via the impedance element 7 (impedance Z) of FIG. The ground metal casing 4 is directly grounded. Further, a capacitance formed between the application electrode 1 and the counter electrode 2 is C, and an impedance therebetween is Zc. Therefore, when plasma is not generated between the application electrode 1 and the counter electrode 2, the impedance Zc is expressed by the following formula (1) using the capacitance C.
Zc = 1 / (2πf · C · j) (1)
Further, when plasma is generated between the application electrode 1 and the counter electrode 2, Zc is represented by a complex number composed of a real part and an imaginary part.

Here, the power supply 8 oscillates power of frequency f [Hz] (low frequency power, high frequency power, VHF power, micro power, etc.), and the oscillating voltage waveform is a substantially sine waveform.
The power generated from the power source 8 is applied to the application electrode 1 through the power transmission line 6, the potential of the application electrode 1 is V, the potential of the counter electrode 2 is Vz, the potential difference between the application electrode 1 and the counter electrode 2 is Vc, and is applied. If the input impedance to the electrode 1 is Zin and the current is I, the equivalent circuit of the electrode unit 5 is represented as shown in FIG.
V = Vc + Vz = I · Zin (2)
Zin = Zc + Z (3)
Vz = I · Z (4)
Vc = I · Zc (5)
Here, using the formulas (2) to (5), the relationship between Vc, Vz and V is as shown in the following formulas (6) and (7).

In the expressions (6) and (7), the voltage Vc between the applied voltage 1 and the counter electrode 2 is increased with respect to the potential V of the applied electrode 1, and at the same time, the potential of the counter electrode 2 with respect to the potential V of the applied electrode 1 Consider the relationship between Zc and Z when Vz is equal or smaller (inequality represented by the following equations (8) and (9)).
｜ Vc ｜ ＞ ｜ V ｜ …… (8)
| Vz | ≦ | V | ...... (9)

From Equation (6) and Equation (8), the relationship between Z and Zc satisfying the relationship between Vc and V expressed by Equation (8) is as follows. The denominator (1 + Z / Zc) in Equation (6) is as shown in FIG. The denominator (1 + Z / Zc) of the equation (6) is given by the following equation (10) because it suffices to be within a circle of radius 1 (not including the line) on the complex plane as shown. Can be represented.
1 + Z / Zc = A · Exp [j · θ] (10)
Where A is a real number of 0 ≦ A <1 and θ is any real number

Further, from the equations (7) and (9), the relationship between Z and Zc satisfying the relationship between Vz and V represented by the equation (9) is the denominator (1 + Zc / Z) in the equation (7). Therefore, the denominator (1 + Zc / Z) of the equation (7) is expressed by the following equation (11) because it is only necessary to be outside the circle of radius 1 (including the line) on the complex plane as shown in FIG. Can be represented.
1 + Zc / Z = B · Exp [j · φ] (11)
However, B is a real number of B ≧ 1, and φ is an arbitrary real number. Therefore, Z can be expressed as follows from the equations (10) and (11).
Z = Zc · (A · Exp [j · θ] -1) (12)

  Since Expression (12) and Expression (13) must be satisfied, the following Expression (14) must be satisfied.

When the above equation (14) is solved for B · Exp [j · φ], equation (15) is obtained.

Here, since B must be B ≧ 1, the following equation (16) holds.
| A · Exp [j · θ] | ≧ | A · Exp [j · θ] -1 | (16)
Therefore, when the equation (16) is changed, the following equations (17-1) to (17-4)
become that way.
| A · Exp [j · θ] | ² ≧ | A · Exp [j · θ] -1 | ² (17-1)
A ² · Exp [j · θ] · Exp [−j · θ] ≧ (A · Exp [j · θ] −1)
(A • Exp [−j • θ] −1) (17-2)
A · Exp [j · θ] + A · Exp [−j · θ] ≧ 1 (17-3)
A · (cos θ + j · sin θ) + A · (cos θ−j · sin θ) ≧ 1 (17-4)
Therefore, the following formula (18) must be established.
A ・ cos θ ≧ 1/2 …… (18)
However, A is a real number of 0 ≦ A <1, and θ is an arbitrary real number.

Conversely, when Z is set to the value represented by the equations (18) and (12) with respect to the impedance Zc formed between the application electrode 1 and the counter electrode 2, the equation (8), Equation (9) can be realized.
Therefore, the voltage Vc between the application electrode 1 and the counter electrode 2 can be increased with respect to the potential difference V between the application electrode 1 and the ground potential, and at the same time with respect to the potential difference V between the application electrode 1 and the ground potential. The magnitude of the potential difference Vz between the counter electrode 2 and the ground potential can be reduced.
Here, the calculation result of the electric field intensity distribution in the vicinity of the imprint electrode 1 and the counter electrode 2 at this time is shown below.

  The application electrode 1 and the counter electrode 2 are both perfect conductors, the distance between the application electrode 1 and the counter electrode is 3 [mm], the distance between the lower surface of the electrode unit 5 and the sample 10 is G = 4.0 [mm], The insulator 3 covering the application electrode 1 and the counter electrode 2 is made of alumina having a relative dielectric constant εr = 9.6, and the voltage V applied to the application electrode 1 has an amplitude | V of a frequency f = 13.56 [MHz]. It is assumed that | = 1.0 [kV] high-frequency voltage. Sample 10 was made of glass having a thickness of 5.0 mm and a relative dielectric constant of 5.5, and the lower side of sample 10 was made of air.

At the same time, the impedance circuit element Z causes Vc = 2V between the applied electrode 1 and the counter electrode 2 (19).
It is assumed that a voltage is generated.
At this time, the value of the impedance circuit element Z that can generate the voltage relationship represented by Expression (19) is expressed as follows from Expression (6).
Z = −Zc / 2 (20)

At this time, the potential difference Vz between the counter electrode 2 and the ground potential is expressed by the equation (7):
Vz = −V (21)
Thus, a voltage is generated in the counter electrode 2 that is equal in magnitude to the voltage V applied to the application electrode 1 and is different in phase by π (180 °). FIG. 6 shows the calculation result of the electric field strength distribution near the sample at this time. However, the center of the center of the three application electrodes 1 in FIG. 1 is X = 0, Z = 0 [mm], the surface of the sample 10 is Y = 0, and the direction from the sample 10 to the electrode unit 5 is Y. Taken in the positive direction of the axis.

  Further, the electric field intensity distribution immediately below the application electrode 1 (X = 0 [mm], Z = 0 [mm], region A ′) and the central portion (X = 5.5) between the application electrode 1 and the counter electrode 2. [Mm], Z = 0 [mm], region B ′), and electric field intensity distribution calculation graph immediately below the counter electrode 2 (X = 11.0 [mm], Z = 0 [mm], region C ′) Is shown in FIG.

Further, for comparison, the counter electrode 2 is grounded without passing through the impedance circuit element Z, and a high frequency voltage having a frequency f = 13.56 [MHz] and | V | = 1.0 [kV] is applied to the application electrode 1. FIG. 8 shows the calculation result of the electric field strength distribution in the vicinity of the sample, and the electric field strength distribution immediately below the application electrode 1 (X = 0 [mm], Z = 0 [mm], region A ″), and the application electrode 1. And the central portion of the gap between the counter electrode 2 (X = 5.5 [mm], Z = 0 [mm], region B ″), and directly below the counter electrode 2 (X = 11.0 [mm], Z = 0 FIG. 9 shows a calculation graph of electric field intensity distribution in [mm], region C ″). FIGS. 8 and 9 show the calculation results obtained by the same grounding method as in the prior art. In this case, between the imprint electrode 1 and the counter electrode 2. The potential difference Vc is Vc = V, and the potential difference Vz between the counter electrode 2 and the ground potential is Vz = 0. It is clear.

As shown in FIGS. 6 and 7, it can be seen that the largest electric field strength of 1.47E6 [V / m] is generated in the recessed portion of the insulator 3 between the application electrode 1 and the counter electrode 2. At the same time, electric field strengths of 1.7E5 and 1.68E5 [V / m] are generated in the vicinity of the surface of the sample immediately below the application electrode 1 and the counter electrode 2, respectively, and the sample 10 immediately below the depression is formed. 0 near the surface of
. An electric field strength of 5E5 [V / m] is generated.

8 and 9, when the counter electrode 2 is grounded without passing through the impedance circuit element Z and a voltage of +1.0 [kV] is applied to the application electrode 1, the application electrode 1 and the counter electrode 2 are applied. It can be seen that only the same electric field strength of 7.45E5 [V / m] is generated in the recessed portion of the insulator 3 between the two. At the same time, only an electric field strength of 0.4 [V / m] is generated on the surface near the sample immediately below the counter electrode 2, but 1.2E5 [V / m] is generated on the surface near the sample immediately below the application electrode 1.
It can be seen that the electric field strength of.

At this time, in the first embodiment shown in FIG. 1, when the applied voltage V of the applied electrode 1 is increased, the insulator between the applied electrode 1 and the counter electrode 2 generating the greatest electric field strength. The atmospheric pressure plasma corresponding to the reaction gas is generated in the hollow portion 3 and the surface of the sample 10 is formed, processed, and surface-treated by the active species generated in the atmospheric pressure plasma. Assuming that the highest electric field strength of the hollow portion of the insulator 3 between the application electrode 1 and the counter electrode 2 is Ep1, and that the highest electric field strength on the surface of the sample 10 is Es1, Ep1 / Es1 = 1.47E6 / 1.7E5. When the counter electrode 2 is grounded without the impedance circuit element Z and a voltage of +1.0 [kV] is applied to the application electrode 1, as shown in FIGS. , Ep1 / Es1 = 7.45E5 / 1 2E5 = 6.2 times to become.

This is because when the counter electrode 2 is grounded via the impedance circuit element Z and the impedance Z is set to a value satisfying Z = −Zc / 2, the voltage V applied to the application electrode 1 is increased. First, plasma is generated in a portion where the highest electric field intensity Ep1 is generated in the hollow portion of the insulator 3 between the application electrode 1 and the counter electrode 2, and the applied voltage to the application electrode 1 at that time is set to Vbd, and thereafter It is shown that when the voltage is further increased, atmospheric pressure plasma is generated on the surface of the sample 10 when the voltage 8.6 times the voltage Vbd is applied to the application electrode 1, and the surface is damaged.

On the other hand, when the counter electrode 2 is directly grounded without passing through the impedance circuit element Z, if the voltage V applied to the application electrode 1 is increased, the depression of the insulator 3 between the application electrode 1 and the counter electrode 2 is similarly performed. Plasma is generated in the portion where the highest electric field strength Ep1 is generated. If the voltage applied to the application electrode 1 at that time is Vbd, the sample is applied when a voltage 6.2 times the voltage Vbd is applied to the application electrode 1. 10 shows that atmospheric pressure plasma is generated on the surface 10 and the surface is damaged.

  Conversely, if the reaction gas type, flow rate conditions, gap G between the electrode unit 5 and the sample 10 are constant, the electric field intensity generated by the plasma is constant, so that plasma is generated on the surface of the sample 10 and the surface of the sample 10 is generated. When a voltage is applied to the application electrode 1 until just before damage is applied to the electrode 1, the method in which the counter electrode 2 is directly grounded without passing through the impedance circuit element Z has an electric field strength of only 6.2 times the electric field strength generated by the plasma. However, when the counter electrode 2 is grounded via the impedance circuit element Z, the electric field intensity (impedance circuit element) is 8.6 times the electric field intensity generated by the plasma. 8.6 / 6.2 = about 1.4 times when not grounded via Z) can be generated in the hollow portion between the application electrode 1 and the counter electrode 2, and the high electric field strength By the decomposition of the reaction gas, it is possible to achieve greater processing speeds.

  Further, the voltage is not applied to the application electrode 1 until plasma is generated on the surface of the sample 10 and the surface of the sample 10 is damaged, and the electric field strength determined from the desired process conditions and the like is set between the application electrode 1 and the counter electrode 2. Even when the counter electrode 2 is generated in the recessed portion between the two, the case where the counter electrode 2 is grounded via the impedance circuit element Z is against the phenomenon in which plasma is generated on the surface of the sample 10 and the surface of the sample 10 is damaged. The safety factor is high (8.6 / 6.2 = about 1.4 times higher safety factor when not grounded via the impedance circuit element Z).

  As described above, when the counter electrode 2 is grounded via the impedance circuit element Z represented by the equation (20), Vc / V = 2 is realized from the equation (19). The ratio (Ep1 / Es1) of the highest electric field strength on the surface of the sample 10 to the highest electric field strength on the surface of the sample 10 (Ep1 / Es1) is Ep1 / Es1 = 8.6. However, when the Vc / V is changed from 1.0 to 2.0, the same electromagnetic field distribution calculation as that shown in FIGS. 6 to 9 is performed to change the electric field intensity ratio (Ep1 / Es1). The results obtained are shown in FIG. 10 and FIG.

However, the value of the impedance circuit element Z inserted at this time is calculated from the equation (6), and at the same time, the value A and the equation (7) shown in the equations (12), (18) to (12). Vz / V was calculated from the above and shown as the dependency on the value A shown in the equation (12). (However, θ in the equation (12) was set to θ = 0.)
10 and 11, when A = 1, Vc = V, Vz = 0, Z = 0, Ep1 / Es1 = 6.2, and the value of the impedance circuit element Z to be inserted is Z = 0. To the connection method shown in the prior art.
In addition, when A = 0.5, Vc = 2V, Vz = −V, Z = −Zc / 2, Ep1 / Es1 = 8.6, which is the same as the case shown in FIGS. .

  Further, as can be seen from FIGS. 10 and 11, Vc and Vz satisfying the expressions (8) and (9) are realized by changing the value A in the range of 0.5 ≦ A <1, and further, the applied electrode The ratio of the highest electric field strength Ep1 and the highest electric field strength Es1 on the surface of the sample 10 (Ep1 / Es1) between the first electrode 1 and the counter electrode 2 is shown in the conventional method. The electric field strength ratio (Ep1 / Es1) at the time of the system can be made larger than 6.2, so that no plasma is generated in the vicinity of the surface of the sample 10, and a higher electric field strength is obtained without damaging the surface of the sample 10. It can be generated in the recessed portion of the insulator 3 between the application electrode 1 and the counter electrode 2, and an increase in the processing speed due to higher decomposition of the reaction gas can be realized.

In the above calculation results, the electric field strength ratio (Ep1 / Es1) was calculated for θ = 0 in the equations (12) and (18). However, even if θ is an arbitrary real number, the equations (12) and (18) If the impedance circuit element Z satisfies (), Vc and Vz satisfying the equations (8) and (9) are realized, and the electric field strength ratio (Ep1 / Es1) is the electric field strength when the connection method is shown in the conventional method. Therefore, a plasma is not generated in the vicinity of the surface of the sample 10, and a higher electric field strength is obtained without damaging the surface of the sample 10. A depression of the insulator 3 between the application electrode 1 and the counter electrode 2 can be obtained. It can be generated in the portion, and an increase in processing speed due to higher decomposition of the reaction gas can be realized.
The above is not limited only to the conditions for performing the calculations shown in FIGS. 6 to 9, but applies to all cases where the internal equivalent circuit uses the electrode unit 5 as shown in FIG.

Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 12 is a schematic view showing a second embodiment of the present invention.
In FIG. 12, 15 is a variable capacitor element, and 16 is an inductance element. Other configurations are the same as those of the first embodiment shown in FIG. That is, the impedance circuit element Z shown in FIG. 1 is realized by connecting the variable capacitor element 15 and the inductance element 16 in series.

Hereinafter, it is shown that the impedance Z satisfying the expressions (12) and (18) can be realized by connecting the variable capacitor element 15 and the inductance element 16 in series.
At this time, since Zc is an impedance formed between the application electrode 1 and the counter electrode 2, when the plasma is not generated, it is expressed by the formula (1), but when the plasma is generated, Zc is It can be represented by the following formula (22).
Zc = R + X · j (22)
However, R is a real number of R ≧ 0, and X is an arbitrary real number.
Further, assuming that the capacitance of the variable capacitor element 15 shown in FIG. 12 is Cv and the inductance of the inductance element 16 is Lv, the impedance Z is constituted by a series circuit of the capacitance Cv and the inductance Lv. Can be represented.

Therefore, from Formula (12), Formula (22), and Formula (23)

Holds.

Here, since Im [Z] can take an arbitrary real number by adjusting Lv and Cv, (A · Exp [j · θ] −1) is shown in FIG. 5 for R and X by various plasmas. It becomes possible to adjust to the region, and for this reason, it is possible to realize the relationship between V and Vc, Vz expressed by the equations (8) and (9).
However, when X = 0, that is, only when the impedance Zc formed between the application electrode 1 and the counter electrode 2 is a pure resistance, the equation (24) becomes the following equation (25):

Must hold.

  That is, (A · Exp [j · θ] −1) must be a pure imaginary number. Here, from (12) and (18), (A · Exp [j · θ] −1) does not take a pure imaginary number, and therefore only when the impedance Zc is a pure resistance, the equations (8) and (8) The relationship between V and Vc, Vz represented by 9) cannot be realized.

  However, as described above, Zc is an impedance formed between the application electrode 1 and the counter electrode 2, and is expressed by the equation (1) when the plasma is not generated, and the plasma is generated even when the plasma is generated. Since the impedance Zc including the impedance does not become a pure resistance, it is expressed by the equations (8) and (9) by the series circuit of the inductance element 16 and the variable capacitor element 15 shown in FIG. The relationship between V, Vc, and Vz can be realized.

  Therefore, the electric field intensity ratio (Ep1 / Es1) can be made larger than the electric field intensity ratio in the connection method shown in the conventional method, so that plasma is not generated in the vicinity of the surface of the sample 10, and the surface of the sample 10 is damaged. Thus, a higher electric field strength can be generated in the recessed portion of the insulator 3 between the application electrode 1 and the counter electrode 2, and an increase in processing speed due to higher decomposition of the reaction gas can be realized.

It is the schematic which shows the structure of the 1st Embodiment of this invention. It is an equivalent circuit inside the electrode unit shown in FIG. It is explanatory drawing which shows the relationship 1 of Z and Zc of FIG. It is explanatory drawing which shows the relationship 2 of Z and Zc of FIG. It is explanatory drawing which shows the relationship 3 of Z and Zc of FIG. It is a calculation result of the electric field strength distribution in the vicinity of the sample when the impedance Z is inserted in FIG. It is a calculation graph of the electric field strength distribution in the vicinity of the sample when the impedance Z is inserted in FIG. It is a calculation result of the electric field strength distribution in the vicinity of the sample when the impedance Z is not inserted in FIG. It is a calculation graph of the electric field strength distribution in the vicinity of the sample when the impedance Z is not inserted in FIG. It is a graph which shows the change of voltage ratio Vc / V, Vz / V. It is a graph which shows the change of electric field strength ratio Ep1 / Es1. It is the schematic which shows the 2nd Embodiment of this invention. It is sectional drawing of an electrode floating type high voltage | pressure floating electrode. It is a calculation result of the electric field strength distribution of FIG. It is a calculation graph of the electric field strength distribution of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Applied electrode 2 Opposite electrode 3 Insulator 4 Ground metal housing 5 Electrode unit 6 Power transmission line 7 Impedance element 8 Power supply 9 Matching box 10 Sample 11 Reactive gas supply port 12 Reactive gas exhaust port 13 Reactive gas flow 14 Atmospheric pressure plasma

Claims (5)

  An electrode unit including an application electrode to which power generated from a power source is applied, a counter electrode facing the application electrode with an insulator interposed therebetween, and an impedance element inserted between the counter electrode and a ground potential The electrode unit is opposed to the sample with a gap, and a reaction gas is locally supplied to a space formed between the electrode unit and the sample, and the applied electrode is separated from the applied electrode by electric power applied to the applied electrode. A plasma processing apparatus that generates plasma between counter electrodes and processes a sample based on a reaction gas. The application electrode and the counter electrode have an impedance Zc therebetween, and the impedance Z of the impedance element is Z = Zc (A · Exp [jθ] −1),
Where θ is any real number,
The plasma processing apparatus according to claim 1, wherein A is a real number satisfying 0 ≦ A <1 and 0.5 ≦ A · cos θ.   The plasma processing apparatus according to claim 1, wherein the application electrode and the counter electrode have an impedance Zc therebetween, and the impedance Z of the impedance element is Z = −Zc / 2. The application electrode and the counter electrode have an impedance Zc between them, and the impedance Z of the impedance element is Z = j · Im [Zc (A · Exp [jθ] −1)]
Where θ is any real number,
The plasma processing apparatus according to claim 1, wherein A is a real number satisfying 0 ≦ A <1 and 0.5 ≦ A · cos θ.   The plasma processing apparatus according to claim 1, wherein the impedance element is formed of a series circuit of an inductance element and a variable capacitance element.