JPH05152097A - Power source matching circuit in plasma etching device - Google Patents

Abstract

PURPOSE:To stabilize electric discharge in a chamber by adjusting the electrostatic capacitances of first and second variable capacitors provided in front and rear of a coil since the electric discharge condition in the chamber caused by a plasma outlet varies, depending upon the size of the chamber, the pressure and kind of treating gas, a source power, the kind of a specimen and the like. CONSTITUTION:In order to stabilize the electric discharge condition in a chamber 7, a type matching circuit 15 as a power source is provided between a table 5 and an amplifier 13 connected to a high frequency oscillator 11. A front variable capacitor 19 and a rear variable capacitor 21 are connected in parallel in front and rear of a coil 17 constituting the circuit 15. In this arrangement, the capacitors 19, 21 are composed finely adjusting first variable capacitors 19A, 21A and roughly adjusting second capacitors 19B, 21B, respectively. A detector 23 is provided between the amplifier 13 and the capacitor 10, for detecting a difference between a plasma input wave and a reflecting wave returned after electric discharge, and accordingly, the electrostatic capacitances of the capacitors are adjusted so that the difference approaches the input wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply matching circuit in a plasma etching apparatus.

[0002]

2. Description of the Related Art Conventionally, an IC chip is manufactured by cutting a wafer formed by printing an electronic circuit into a plurality of dice and adhering the dice to a frame with, for example, an adhesive. In order to analyze the failure of the test piece such as the IC chip, it is necessary to remove the passivation film on the surface of the IC chip. A plasma etching apparatus is known for removing this film.

Recently, a plasma etching apparatus for manufacturing line analysis has been put into practical use for the purpose of analyzing a wafer before it becomes an IC chip. As a main configuration of a plasma etching apparatus for analyzing a failure of a sample such as a wafer or an IC chip, a table serving as a cathode is provided on a base, and a sample such as an IC chip or a wafer is provided on the table. Is placed.
Moreover, a chamber having an anode on the lower surface is provided on the table so as to seal the sample.

Thus, the sample is etched by generating plasma between the anode and the cathode, the passivation film on the surface of the chip is removed, and the electronic wiring is exposed. Analysis will be checked.

As a power supply matching circuit in this plasma etching apparatus, a coil is connected in series between a table as a cathode and an amplifier connected to a high frequency oscillator, and fine adjustments are made before and after the coil. The variable capacitor of and the variable capacitor for coarse adjustment are connected in parallel.

[0006]

By the way, in the power source matching circuit in the above-mentioned conventional plasma etching apparatus, the inside of the chamber depends on the size of the chamber, the pressure of the processing gas, the type, the power of the supplied power source, the type of the specimen, and the like. Since the discharge state of 1 changes, it is necessary to make this discharge state constant. As this means, the inductance capacitance of the coil in the matching circuit is made constant in advance, and each capacitor is operated by an individual motor in order to change the capacitances of the fine adjustment capacitor and the coarse adjustment capacitor before and after the coil. ing. In other words, the electrostatic capacity of each capacitor must be adjusted every time the discharge state changes with a total of four motors, which is difficult to adjust and the manufacturing cost is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply matching device in a plasma etching device, which facilitates adjustment of a dense capacitor and a coarse capacitor and reduces manufacturing cost in order to solve the above problems.

[0008]

In order to achieve the above object, the present invention aims to place a test piece on a table which is one of the electrodes provided on a base and to seal the test piece. A chamber provided with the other electrode on the lower surface is provided on the table, and a plasma is generated between the one electrode and the other electrode to generate a plasma between the one electrode and the plasma etching apparatus for etching the sample, A coil is connected in series between the electrode table and the amplifier connected to the high-frequency oscillator, and first and second variable capacitors for fine adjustment are provided before and after the coil, respectively.
The second variable capacitor for coarse adjustment is connected in parallel,
A power supply matching circuit in a plasma etching apparatus, in which a first variable capacitor and a second variable capacitor are connected to each other to perform variable adjustment of the first variable capacitor and the second variable capacitor, and a drive motor is interlocked and connected to the first variable capacitor. Configured.

[0009]

By employing the power supply etching circuit in the plasma etching apparatus of the present invention, the plasma oscillated by the high frequency oscillator is amplified by the amplifier and then output to the plasma etching apparatus through the power supply matching circuit. That is, the inside of the chamber is in a discharge state due to plasma between the table as one electrode and the other electrode provided in the chamber, and the test gas on the table is etched by the processing gas introduced into the chamber. The passivation film on the surface of the specimen is removed.

The discharge state in the chamber due to the output of the plasma depends on the size of the chamber, the pressure of the processing gas, the type,
Since it changes depending on the power of the power supply, the type of test piece, etc., the first and second variable capacitors provided before and after the coil should be adjusted to one drive motor to adjust the capacitance of each capacitor. By doing so, matching is performed and the discharge state in the chamber is stabilized.

[0011]

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

Referring to FIG. 2, the plasma etching apparatus 1 is provided with a box-shaped base 3 on which a wafer having a diameter of, for example, about 4 to 8 inches or a test piece such as an IC chip is provided. A table 5 for mounting and supporting S is provided. A chamber 7 is provided on the table 5 so as to surround (close) the sample S placed and supported on the table 5. In addition, in this embodiment, the table 5 serves as a cathode and the lower surface of the upper portion of the chamber 7 serves as an anode. Moreover, this anode is grounded.

A processing gas such as chlorofluorocarbon (CF ₄ ) is supplied into the chamber 7 from above the chamber 7 through a pipe (not shown) through a cylinder (not shown), and vacuum suction is performed from the upper surface of the base 3 so that the chamber 7 is evacuated. Has been done. In this state, when plasma is applied to the cathode of the table 5, the inside of the chamber 7 becomes a discharge state,
For example, the passivation film applied to the surface of the sample S placed and supported on the table 5 is removed by etching with a processing gas such as CFC gas. That is, since the electronic wiring is exposed on the surface of the sample S, the failure analysis is checked.

A power supply matching circuit (π type matching circuit) 15 is provided between the table 5 and the amplifier 13 connected to the high frequency oscillator 11 in order to stabilize the discharge state in the chamber 7. ing. That is, the coil 17 is connected in series between the table 5 and the amplifier 13, and the front variable capacitor 19 and the rear variable capacitor 21 are connected in parallel before and after the coil 17.

Moreover, front and rear variable capacitors 19 and 21
Are the first variable capacitors 19A and 21 for fine adjustment.
A and second variable capacitors 19B and 21B for coarse adjustment. The coil 17 has a fixed number of turns and a predetermined shape so that the discharge state in the chamber 7 can be adjusted only by adjusting the first and second variable capacitors 19A, 21A; 19B, 21B in advance.

A detector 23 is connected in parallel between the amplifier 13 and the front variable capacitor 19.
The difference between the input wave of the plasma amplified in 3 and the reflected wave returned after being discharged in the chamber 7 is the detector 23.
Is detected by. The capacitances of the first and second variable capacitors 19A, 21A; 19B, 21B are adjusted so that the difference detected by the detector 23 approaches the input wave. The point is to adjust the reflected wave as close to zero as possible so as to match it and try to match it.

As a concrete structure of the front and rear variable capacitors 19 and 21, as shown in FIG. 1, front and rear variable capacitors 19A and 19B; 2 on the base 25.
Main body frames 27A and 27B with built-in 1A and 21B;
29A and 29B are provided. Also, the base 2
Drive motors 35 and 37 are attached to the right side above 5 via brackets 31 and 33. This drive motor 3
Pinions 39, 41 are attached to the output shafts of 5, 37.

On the other hand, the main body frames 27A and 27B;
Rotation shafts 43A, 43B; 45A, 45B are respectively attached to the first and second variable capacitors 19A, 19B; 21A, 21B built in 29A, 29B.
The rotary shafts 43A, 43B; 45A, 45B project to the right of the main body frames 27A, 27B; 29A, 29B. Then, the protruding rotation shafts 43A, 45
Sprockets 47 and 49 and gears 51 and 53 are attached to A. Further, sprockets 55, 57 and cams 59, 61 are mounted on the rotary shafts 43B, 45B.

A chain 63 is wound around the sprockets 47 and 55 in a loose state. Similarly, a chain 65 is wound around the sprockets 49 and 57 in a loose state. The pinion 3 is attached to the gears 51 and 53.
9, 41 are meshed.

Cam grooves 59G and 61G are provided in a part of the outer peripheral portions of the cams 59 and 61. On the other hand, detection devices 67 and 69 are mounted on the base 25, and the detection devices 67 and 69 are provided with switches 71 and 73 composed of rollers. These switches 71 and 73 are cams 59 and 61 by the urging force of springs or the like.
Is in contact with the outer peripheral surface of the.

With the above structure, when the drive motors 35 and 37 are driven, the pinions 39 and 41 are rotated via the output shaft. The rotation of the pinions 39 and 41 causes the sprockets 47 and 49 to rotate via the gears 51 and 53 and the rotation shafts 43A and 45A. During the period from the loose state of the chains 63, 65 to the tension, the sprocket 4
By rotating 7, 49, the first variable capacitors 19A, 21A are actuated to operate the first variable capacitors 19A, 21A.
The electrostatic capacitances of A and 21A change, and fine adjustment is performed.

Further, when the sprockets 47 and 49 are rotated, the chains 63 and 65 are tensioned and run, so that the sprockets 55 and 57 are rotated. By rotating the sprockets 55 and 57, the second variable capacitors 19B and 21B are actuated to change the electrostatic capacities of the second variable capacitors 19B and 21B, and coarse adjustment is performed.

The first and second variable capacitors 19A, 1
The capacitances of 9B and 21A and 21B may be adjusted simultaneously or individually. As the sprockets 55 and 57 rotate, the cam 5
9 and 61 are also rotated at the same time, and the switches 71 and 73 are fitted into the cam grooves 59G and 61G, whereby the origin position is set.

In this way, one drive motor 35, 37
Using the first and second variable capacitors 19A, 19B
By operating 21A and 21B, it is possible to easily adjust the coarseness and the fineness of the electrostatic capacitance. Moreover, in the past,
In the present embodiment, the fine adjustment is performed by one drive motor (two in total), but in this embodiment, the coarse and fine adjustments can be performed by one drive motor, so that the cost is reduced. Can be planned.

Also, since the discharge state in the chamber 7 changes depending on the size of the chamber 7, the pressure and type of gas, the power of the power supply, the type of specimen, and so on, the plasma changes as the discharge state changes. The first and second variable capacitors 19A, 21A;
The electrostatic capacities in B and 21B can be adjusted roughly and densely to easily match, and the discharge state in the chamber 7 can be controlled to be always stable.

Further, even while the specimen S is being etched, matching can be easily performed.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes. In this embodiment, the first and second variable capacitors 19A and 21A; 19B and 21
As the coarse / fine adjustment in B, the chain is wound around the sprocket in a loosened state, but it may be wound around the pulley in a loosened timing belt, or a plurality of gears are combined. It is also possible to use the play between the gears.

[0028]

As can be understood from the above description of the embodiments, according to the present invention, since the structure is as described in the claims, one drive motor is used, and By operating the first and second variable capacitors for coarse adjustment, it is possible to easily adjust fine and coarse electrostatic capacitance. Therefore, depending on the size of the chamber, the pressure and type of gas, the power of the power supply, the type of specimen, etc., it is possible to easily match even if the discharge state in the chamber changes, and always control in a stable state. be able to.

Further, in the prior art, one drive motor is used for each of the coarse and fine adjustments, whereas the coarse and fine adjustments can be performed by one drive motor, thus reducing the cost. Can be planned.

[Brief description of drawings]

FIG. 1 shows a main part of the present invention.
It is a perspective view of an example showing an adjusting mechanism which adjusts a 2nd variable capacitor.

FIG. 2 is an explanatory diagram showing a main part of a plasma etching apparatus and a power supply matching circuit.

[Explanation of symbols]

 1 Plasma Etching Device 5 Table 7 Chamber 11 High Frequency Oscillator 13 Amplifier 15 Power Supply Matching Circuit 17 Coil 19A, 21A First Variable Capacitor 19B, 21B Second Variable Capacitor 35, 37 Drive Motor 47, 49 Sprocket 55, 57 Sprocket 63, 65 Chain S specimen

Claims (1)

[Claims] 1. A specimen is placed on a table which is one of the electrodes provided on a base, and a chamber having the other electrode on the lower surface is provided on the table to seal the specimen. In a plasma etching apparatus that performs etching processing on the sample by generating plasma between the one electrode and the other electrode, between the table serving as the one electrode and an amplifier connected to a high-frequency oscillator. , A coil is connected in series, and a first variable capacitor for fine adjustment and a second variable capacitor for coarse adjustment are connected in parallel before and after the coil, and the first variable capacitor and the second variable capacitor are provided. The first variable capacitor and the second variable capacitor are connected to each other for variable adjustment of, and the drive motor is interlocked and connected to the first variable capacitor. A power supply matching circuit in a plasma etching apparatus characterized in that