JPH05152098A - Power source matching circuit in plasma etching device - Google Patents

Abstract

PURPOSE:To enlarge the allowable range chamber by amplifying plasma oscillated by a high frequency oscillator with the use of an amplifier, and thereafter, by delivering the plasma to a plasma etching device through a power source matching circuit so as to cope with an etching adjustment even though a process condition is greatly changed. CONSTITUTION:In order to stabilize the electric discharge condition in a chamber 7 constituting a etching device, a type matching circuit 15 as a power source is provided in series 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 provided with finely adjusting first variable capacitors 19A, 21A and roughly adjusting second capacitors 19B, 21B, in series, respectively. A detector 23 is provided between the amplifier 13 and the capacitor 10, in parallel, for detecting a difference between a plasma input wave and a reflecting wave returned after electric discharge in the chamber 7, and accordingly, the reflecting wave is minimized, so as to carry out the matching.

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 test piece such as a wafer or an IC chip, a table serving as a cathode is provided on a base, and the test piece such as an IC chip or a wafer is placed on the table. 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. The analysis will be checked for defects and failures.

As a power supply matching circuit in this plasma etching apparatus, a fixed coil is connected in series between a cathode table and an amplifier connected to a high-frequency oscillator, and variable coils are provided before and after the coil. Capacitors are connected in parallel.

[0006]

By the way, in the power supply matching circuit in the above-mentioned conventional plasma etching apparatus, processing conditions such as 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, etc. Since the discharge state in the chamber changes due to this, it is necessary to keep this discharge state constant. As this means,
The inductance capacitance of the coil in the matching circuit is made constant in advance, and the capacitance of the variable capacitors before and after the coil is changed to adjust the matching. Therefore, the matching adjustment can be performed when the change in the processing condition is slight, but the matching adjustment cannot be performed when the change in the processing condition is greatly changed, and the allowable range is narrow. was there.

In order to solve the above problems, an object of the present invention is to provide a power supply in a plasma etching apparatus in which a matching adjustment can be performed even if a change in processing conditions greatly changes so that an allowable range is widened. It is to provide a matching device.

[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 plasma etching apparatus in which a coil is connected in series between a table that serves as an electrode and an amplifier connected to a high-frequency oscillator, and variable capacitors are connected in parallel before and after the coil and the coil is variably provided The power supply matching circuit in was constructed.

[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 processing conditions such as the power of the power supply and the type of specimen, it is usually matched by adjusting the capacitance of the variable capacitors installed before and after the coil, but when the processing conditions change significantly. Can be easily matched by adjusting the reactance of the coil.

[0011]

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

Referring to FIG. 1, a 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 this embodiment, the table 5 serves as an anode and the lower surface of the upper portion of the chamber 7 serves as a cathode. Moreover, this cathode 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 anode 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, an analysis check for defects and failures is performed.

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 variable coil 17 is connected in series between the table 5 and the amplifier 13, and the coil 17 is also connected in series.
Front variable capacitor 19, front variable capacitor 2 before and after
1 are connected in parallel.

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.

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, and the reactance value of the variable coil 17 is also adjusted. It is supposed to be adjusted. The point is to adjust the reflected wave as close as possible to zero and try to match it.

As a concrete structure of the front and rear variable capacitors 19 and 21, as shown in FIGS. 2 and 3, the front and rear variable capacitors 19A and 19A are arranged on the base 25.
19B; body frame 27 incorporating 21A and 21B
A, 27B; 29A, 29B are provided. Also,
Drive motors 35 and 37 are attached to the right side of the base 25 via brackets 31 and 33. Pinions 39 and 41 are attached to the output shafts of the drive motors 35 and 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.

Further, since the discharge state in the chamber 7 changes depending on the size of the chamber 7, the pressure and type of the processing gas, the power of the power supply, the type of the sample S, etc., the discharge state changes. , The first and second variable capacitors 19A, 21A; 1 so as to minimize the reflected wave of plasma.
The electrostatic capacities in 9B and 21B can be adjusted roughly and finely to easily match, and the discharge state in the chamber 7 can always be controlled to a stable state.

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

In this embodiment, the coarse and fine adjustments of the first and second variable capacitors 19A, 21A; 19B and 21B are carried out by winding the chain on the sprocket in a loosened state. The timing belt may be wound around the pulley in a loosened state, or a combination of a plurality of gears may be used to make use of the play between the gears.

As a concrete structure of the variable coil 17, as shown in FIGS. 2 and 4, a U-shaped bracket 75 is provided at a lower portion of the base 25.
In addition, a plurality of slide rails 77 extending in the left-right direction in FIG. 4 are provided in the bracket 75. A slide table 79, which is guided by the slide rail 77 and is movable in the left-right direction, is provided on the slide rail 77. The right side of the slide table 79 has a rack 8 extending in the left-right direction.
1 is integrally provided.

On the other hand, a table driving motor 85 is attached to the lower portion of the base 25 via a U-shaped bracket 83. A pinion 89 is attached to the output shaft 87 of the table driving motor 85. The rack 81 is meshed with the pinion 89.

A core mounting plate 91 is mounted on the right side of the slide table 79, and a core 93 is provided in the core mounting plate 91. Also, the core 9
A coil 17 having fixed ends at both ends, which is omitted in the figure, is fixed on the extension of the coaxial line 3.

With the above configuration, the table driving motor 8
5 is driven, the pinion 89 is passed through the output shaft 87.
Is rotated. The rack 8 is rotated by the rotation of the pinion 89.
1 is moved left and right. By the movement of the rack 81, the slide table 79 is guided by the slide rail 77 and moved in the left-right direction. By moving the slide table 79, the core 93 is passed through the core mounting plate 91.
Is the coil 1 fixed on the coaxial line extension of the core 93.
7 will be approached and separated.

Therefore, with respect to the coil 17, the core 93
It is possible to adjust the reactance value by moving the and moving away from each other. Therefore, even when the processing conditions greatly change depending on the size of the chamber 7, the pressure and type of the processing gas, the power of the power supply, the type of the sample S, etc., the capacitances of the capacitors 19 and 21 are adjusted. In addition, by adjusting the value of the inductance of the coil 17, matching can be easily performed. That is, by adjusting the inductance value of the coil 17 rather than just adjusting the electrostatic capacitances of the capacitors 19 and 21, it is possible to cope with a large change in the processing conditions.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes. In the present embodiment, an example has been described in which the core 93 is moved toward and away from the coil 17, but it is also possible to fix the core 93 and move the coil 17 toward and away from each other.

[0034]

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, the variable capacitor is used in the matching circuit in the plasma etching apparatus. By adjusting the capacitance of the coil and the reactance value in the coil, the processing conditions depending on the size of the chamber, pressure of the processing gas, type, power of the power supply, type of specimen, etc. Even if there is a change, matching can be easily performed, and a large change in processing conditions can be dealt with.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a main part of the present invention and showing a main part of a plasma etching apparatus and a power supply matching circuit.

FIG. 2 is a plan view showing portions of a variable capacitor and a variable coil in an etching circuit.

FIG. 3 is a perspective view showing a specific configuration for roughly and finely adjusting the variable capacitor in FIG.

FIG. 4 is a perspective view showing a specific configuration for adjusting the variable coil in FIG.

[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 79 Slide Table 81 Rack 85 Table Drive Motor 89 Pinion 93 Core 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 power supply matching circuit in a plasma etching apparatus, wherein coils are connected in series and variable capacitors are connected in parallel before and after the coils, respectively, and the coils are variably provided.