JP2867616B2 - High frequency voltage detector for film forming equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for detecting a high-frequency voltage applied to a high-frequency electrode in a film forming apparatus such as a high-frequency excitation type plasma CVD apparatus.

[Conventional technology]

As an apparatus for forming a thin film on a substrate, a sputtering apparatus, a plasma CVD apparatus, or the like has been conventionally used.
In a conventional plasma CVD system, a high-frequency electrode is placed in the center of the chamber, ground electrodes are provided on both sides of the chamber, and a substrate is mounted on each of the ground electrodes. An apparatus is provided.

Such a conventional vertical double-sided film forming apparatus is shown in FIG.
In this film forming apparatus, first and second high-frequency electrodes 2 and 3 are arranged in a chamber 1 at predetermined intervals. Each of the high-frequency electrodes 2 and 3 is electrically insulated via an insulating member or the like. The substrates 4 and 5 can be arranged so as to face each of the high-frequency electrodes 2 and 3. In addition, earth shields 6 and 7 are provided around the high-frequency electrodes 2 and 3, respectively. Each high-frequency electrode 2, 3 has a variable capacitor
8, 9 are connected. These variable capacitors 8, 9 are connected to a high-frequency power supply 10 via a matching circuit 11.

In such a device, the intensity of the plasma generated between each of the high-frequency electrodes 2, 3 and the substrate 4, 5 can be independently controlled by appropriately changing the capacity of the variable capacitors 8, 9 respectively. .

In the apparatus shown in FIG. 4, the high-frequency power output from the high-frequency power supply 10 is supplied to two high-frequency electrodes 2 and 3 in the chamber 1.
The capacitance of the variable capacitors 8 and 9 is adjusted in order to uniformly supply the high-frequency electrodes. In this case, the high-frequency voltages at the introduction points N and M of the high-frequency electrodes 2 and 3 are adjusted to be equal.

[Problems to be solved by the invention]

As described above, in order to adjust the plasma intensity of the two electrodes 2 and 3 and the electrodes 4 and 5, it is necessary to measure the high-frequency voltage at the introduction points N and M. Therefore, a high-frequency voltage detector may be connected to each of the N and M points. In general, when voltage detection is performed, the input impedance Z1 of the voltage detection unit 12 is changed to the input impedance of the circuit under test 13 as shown in FIG. It must be sufficiently large compared to the impedance Z2.

However, the introduction points N and M of the apparatus as shown in FIG. 4 are not only a high-frequency introduction part but also a gas introduction part, and there is no room for installing a high-frequency voltage detector. Therefore, the conductor single wires 14 and 15 must be connected to the N and M points, and the detector must be connected via these conductor single wires 14 and 15.

However, when the circuit to be measured and the voltage detecting section are connected via the conductor single wires 14 and 15, as shown in FIG.
The input impedance Z3 of the voltage detector including the conductor single wires 14, 15 greatly changes depending on the length of the conductors 4, 15 or the gap between the conductor single wires 14, 15 and the ground. Therefore, in some cases, the impedances Z3 and Z2 have substantially the same value, causing a large error when measuring the high-frequency voltage with the voltage detector.

An object of the present invention is to provide a high-frequency voltage detecting device of a film forming apparatus capable of accurately detecting a high-frequency voltage applied to an electrode and supplying power to two electrodes in a well-balanced manner.

[Means for solving the problem]

The high-frequency voltage detection device of the film forming apparatus according to the present invention applies a high-frequency voltage to the first and second electrodes from a high-frequency power supply,
It is used in a film forming apparatus for forming a film by generating a plasma discharge between each substrate and a substrate facing each electrode. And it has a 1st, 2nd measuring device, and a 1st, 2nd coaxial line.

The first and second measuring devices are for measuring high-frequency voltages applied to first and second electrodes, and the first and second coaxial lines are integers of half-wavelengths of the high-frequency wave to be measured. It has twice the length, and connects the high-frequency voltage introduction section to the first and second electrodes with the first and second measuring instruments.

[Action]

In the present invention, as shown in FIG. 3, the voltage detector and the high-frequency voltage introducing section to the electrode are connected by a coaxial line having a length that is an integral multiple of a half wavelength of the high frequency to be measured. Input impedance of voltage detector including line
Z4 becomes equal to the input impedance Z1 of only the voltage detection unit. That is, this is equivalent to a case where the high-frequency voltage detection unit is directly connected to the measured point.

Thereby, even when there is no space for installing the voltage detection unit as in a vertical double-sided film forming apparatus, for example, a measurement result with very little error can be obtained, and the intensity of the two plasma discharges can be balanced. Can be adjusted.

〔Example〕

FIG. 1 shows a vertical double-sided film forming apparatus and a high-frequency voltage detecting apparatus according to an embodiment of the present invention.

In FIG. 1, for example, high-frequency electrodes 21 and 22 made of stainless steel are arranged in a film-forming chamber 20 in a vertical posture. Both electrodes 21 and 22 are kept at a predetermined interval by an insulating member. Earth shields 23 and 24 are arranged around each of the high-frequency electrodes 21 and 22. In the film forming chamber 20, heaters 25 and 26 are disposed on both left and right side walls. In addition, variable capacitors 27 and 28 are connected to each of the high-frequency electrodes 21 and 22, and the variable capacitors 27 and 28 are both connected to a high-frequency power supply 31 via a matching circuit 29 and a coaxial line 30. Note that the variable capacitors 27 and 28 are provided in the intermediate box 32.

A substrate cart 33 can be carried into the film forming apparatus 20 in a direction perpendicular to the paper surface of FIG. The substrate cart 33 functions as a ground electrode, and the high-frequency electrodes 21 and 2
Substrates 34 and 35 are mounted in a vertical posture so as to face each of the two.

Coaxial lines 36 and 37 are connected to high-frequency voltage introducing portions N and M to the high-frequency electrodes 21 and 22, respectively. Also coaxial line 3
A coil-shaped part is formed in a part of 6,37. The other ends of the coaxial lines 36 and 37 are connected to RF detectors 38 and 39 for measuring high-frequency voltages applied to the electrodes 21 and 22, respectively. A gas pipe 40 for introducing a gas is also connected to the high-frequency voltage input section of the film forming apparatus 20.

FIG. 2 shows a block diagram of the high-frequency voltage detecting device. As shown in this figure, coaxial lines 36 and 37 are connected between the RF detecting sections 38 and 39 and the introduction sections of the electrodes 21 and 22 as the circuits to be measured. As shown in FIG. 3, the half-wavelength of the high frequency to be measured (λ /
The length is an integral multiple of 2).

In the high-frequency voltage detection device configured as described above, RF
The input impedance Z1 of the detection units 38 and 39 and the coaxial lines 36 and 37
And the differential component (see FIG. 2), which is a measurement signal, is equal to the impedance Z4 including the RF detection units 38 and 39.
Is directly connected to the high frequency introducing sections N and M. Although the coaxial lines 36 and 37 have a coil-shaped part, the number of turns of the center conductor and the outer conductor of the coaxial lines 36 and 37 is the same, so there is no effect on the differential component. Never.

Here, it will be described in detail that when the length of the coaxial line is an integral multiple of a half wavelength of the high frequency to be measured, the impedance including the coaxial line is equal to the impedance not including the coaxial line.

Here, the reflection coefficient _A at the line A shown in FIG.
The relationship with the reflection coefficient _B at the portion _B is represented by _A = _B・ e− ^2jKL (1) where l is the length between the two. Here, since the phase constant K is K = 2π / λ (2), λ / 2 = π / K (3), and l = n · λ / 2 = n · π / K (4) ). Therefore, substituting (4) into _{(1), A = B ·} E -2jKnπ / K _{, and} becomes an ^{_{A = B · e -2njπ = B}} .

Thus, the reflection coefficients _A and _B become equal. That is, the input impedance Z4 of the part A is equal to the input impedance Z1 of the part B.

Although the in-phase component as shown in FIG. 2 causes an error at the time of measurement, since a part of the coaxial lines 36 and 37 is formed in a coil shape, the in-phase component can be reduced by the coil portion. More accurate voltage detection can be performed.

〔The invention's effect〕

As described above, in the present invention, if there is a space around the measured point where a coaxial line can be connected, the high-frequency voltage introduced to the electrode can be accurately and easily measured with a very small error.
The adjustment of the plasma intensity between each electrode and the substrate can be reliably performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a vertical double-sided film forming apparatus employing a high-frequency voltage detecting device according to an embodiment of the present invention, FIG. 2 is a schematic block diagram of the high-frequency voltage detecting unit, and FIG. FIG. 4 is a view for explaining the input impedance of the high-frequency voltage detector, FIG. 4 is a schematic vertical sectional view of a film forming apparatus employing a conventional high-frequency voltage detector, and FIG. 5 is a block diagram of the high-frequency voltage detector. FIG. 6 is a diagram for explaining a conventional problem. 21,22 high-frequency electrode, 31 high-frequency power supply, 34,35 substrate, 36,37 coaxial line, 38,39 high-frequency voltage detector.

Claims (1)

(57) [Claims] A high-frequency voltage is detected in a film-forming apparatus for applying a high-frequency voltage from a high-frequency power source to first and second electrodes to generate a plasma discharge between the first and second electrodes and a substrate facing each electrode to form a film. An apparatus, comprising: first and second measuring devices for measuring a high frequency voltage applied to the first and second electrodes; and a length having an integral multiple of a half wavelength of the high frequency to be measured. A first and second high-frequency voltage introducing section to the second electrode;
And a first and a second coaxial line for connecting to the measuring device of (1).