JPH0689463B2 - Trimming method for electronic devices by sputtering - Google Patents

Description

TECHNICAL FIELD The present invention relates to a trimming method by sputter etching in which an electronic element such as a surface acoustic wave element is trimmed by using a high frequency sputter etching apparatus.

“Prior Art” When manufacturing an electronic device, a so-called trimming process for adjusting the characteristics of the electronic device is often introduced at the final stage of the manufacturing. For example, in a surface acoustic wave (SAW) element, frequency trimming is performed to adjust its operating frequency to a predetermined value. As a method of trimming the SAW element, a method of performing sputter etching on the surface of the substrate on which the SAW element is formed is effective.
As a means for sputter etching, a sputter etching technique using high frequency discharge (RF sputter etching) is useful.

However, in the conventional RF sputter etching, it was difficult to monitor the characteristics of the element to be processed while the etching was in progress. The reason is that in RF sputter etching, the sample to be etched is placed on the side of the target electrode, but a high-frequency voltage is applied between the target electrode and the grounded counter electrode to cause discharge. This is because the potential of the target electrode is biased to a DC negative potential of 100 V or more with respect to the ground during discharge, and thus the element to be processed of the sample also has a negative potential with respect to the ground. Due to such a bias potential, the measuring device such as an oscillator used at the ground potential and the element to be processed cannot be directly connected by a coaxial cable or the like.

For this reason, conventionally, it has been usual to take a method in which the element to be processed is separated from the measuring instrument while the trimming is in progress, and the discharge is stopped during the process to measure the characteristics. Also,
If it is indispensable to monitor the element characteristics while trimming is in progress, use a cable to disconnect both the earth side and signal side conductors of the cable connecting the element and the measuring instrument in a direct current manner. A method of connecting using a pad was required. However, in this case, there is a problem that the characteristics of the element cannot be accurately monitored due to the influence of the characteristics of the pad. Also,
When the element to be processed needs to measure the DC characteristics, such as a resistance element, it is not possible to use the above-mentioned DC cutoff pad, so it is impossible to monitor the characteristics while trimming is in progress. It was

"Means for Solving Problems" The present invention relates to a characteristic adjusting process of an electronic element using high frequency sputter etching, in which at least one conductor of an electric cable connecting the element to be processed and a measuring device is connected to the element to be processed. The target electrode is connected to the target electrode on which is attached and the electric cable that connects the element to be processed and the measuring instrument is bent to form an inductance, so that the target electrode has the same potential as the measuring instrument in terms of DC The target electrode applies a sufficient high frequency bias to the measuring device (earth) in response to the high frequency input, so that the element to be processed is sputter-etched and at the same time the characteristics of the element to be processed are monitored.

"Embodiment" FIG. 1 shows an embodiment of the present invention. A target electrode 12 is provided in the lower part of the bell jar 11, an opening 13 is formed in a part of the upper surface of the target electrode 12, and an element 14 to be processed is attached to the target electrode 12 immediately below the opening 13. An upper electrode 15 is provided above the bell jar 11 so as to face the target electrode 12. The target electrode 12 is electrically insulated from the metal bell jar 11, and the discharging high frequency voltage from the high frequency power supply 16 is applied between the target electrode 12 and the ground via the matching circuit 17. The electric terminals of the element to be processed 14 are electric cables 18a, 18
It is connected to the measuring device 19 through b. The bell jar 11 is grounded, and a gas inlet 21 and an exhaust port 22 are provided.

In the present invention, at least one of the electric cables 18a, 18b
One conductor, in this example a coaxial outer conductor, is electrically connected to the target electrode 12, and the electrical cables 18a, 18b are curved, i.e. coiled, between the element 14 to be processed and the measuring device 19. And the inductance element 23 is configured.

In the configuration of FIG. 1, a high frequency voltage is applied to the target electrode 12 from a high frequency source 16 through a matching circuit 17. On the other hand, the upper electrode 15 is electrically insulated from the bell jar 11 in this example, and is electrically floating without being connected to the ground. If the element to be processed 14 is, for example, a surface acoustic wave filter, its substrate surface is placed facing upward, and its input / output terminals are connected to the measuring instrument 19 through the electric cables 18a and 18b for measurement. The electric cables 18a and 18b are grounded through one of the conducting wires, that is, their outer conductors are in contact with the target electrode 12 if they are coaxial wires, and are further grounded through the ground terminal of the measuring device 19.

A gas for etching is introduced into the bell jar 11, and a high frequency voltage is applied to the target electrode 12 while maintaining an appropriate pressure. As the frequency of the high frequency voltage, 13.56M for industrial use
Although Hz is normally used, since the target electrode 12 is grounded through the inductance element 23 formed by the electric cables 18a and 18b, the inductance element 23 acts as reactance with respect to this high frequency voltage, and the matching circuit 17 is appropriate. If adjusted to, a voltage sufficient for discharge is applied to the target electrode 12, and plasma is generated in the bell jar 11 due to high frequency discharge of gas.

As the inductance element 23, an electric cable 18a, 18b is used which has a radius of 40 to 50 mm and is wound in a coil shape of 15 to 20 turns. confirmed.

On the other hand, since the upper electrode 15 is in an electrically floating state, it can be charged to a positive potential with respect to the ground and become a plasma potential. On the other hand, since the target electrode 12 is grounded in terms of direct current, the positive ions of the gas generated by the discharge are accelerated toward the target electrode 12 and collide with the surface of the processed element 14 through the opening 13. Etching is performed. Since the element to be processed 14 is connected to the measuring device 19 through the electric cables 18a and 18b, the characteristics of the element to be processed 14 can be observed even during the etching of the element to be processed 14, so that The characteristics can be precisely adjusted.

When measuring the characteristics of the processed element 14, it is feared that the high frequency power for discharge or the noise of the plasma may affect the measurement accuracy, but according to the experiment, the measured frequency is separated from the frequency of the high frequency for discharge to some extent. If so, there is almost no problem, and if a filter for removing the high frequency for discharge is inserted between the electric cables 18a, 18b and the measuring device 19, a better measurement is possible. Also, when trimming a SAW filter that operates in an extremely high frequency band of 1 GHz or higher, it is necessary to finely control the etching amount.In that case, attach a mesh such as stainless steel to the opening 13 of the target electrode 12. Is effective (Uno, Onuki "Frequency adjustment of SAW devices by sputter etching",
Proceedings of the 6th Symposium on Fundamentals and Applications of Ultrasonic Electronics, Proceedings No.P-15, December 1985,) In such a case, it is effective for noise removal from plasma due to the shielding effect of the mesh. Is. Fig. 2 shows the 1.8 GHz band SA in the un-discharging state A and the trimming B.
An example of W filter characteristic measurement is shown. From this example, it is clear that the characteristics measurement during trimming is hardly affected by high frequency and plasma noise. In Fig. 2, the vertical axis is 1 dB / scale and the horizontal axis is 500 kHz / scale.

Although the upper electrode 15 is in an electrically floating state in the above description, it is possible to perform etching even if the upper electrode 15 is connected to the bell jar 11 and is at the ground potential. In that case, since the effect of accelerating the ions due to the bias potential is reduced, the etching is mainly performed only by the thermal ion in the plasma, that is, among the ions moving in a random direction, only by the particle component having the moving direction toward the processed element 14. As the etching proceeds, the etching rate decreases, but it goes without saying that the characteristic measurement during the etching can be performed in the same manner as described above.

[Advantages of the Invention] As described above, the method for trimming an electronic element according to the present invention is a very simple method and is capable of accurately measuring the characteristics of an electronic element during trimming. Moreover, since the element characteristics can be precisely adjusted, it is useful for manufacturing various electronic elements including the SAW element.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a sputter etching apparatus used in an embodiment of the present invention, and FIG. 2 is a diagram showing electronic element characteristics in an untrimmed state and characteristics during electronic element trimming by the method of the present invention. It is a figure which shows the example of a monitoring.

Claims (1)

[Claims] 1. A target electronic part of a sputter etching apparatus using high-frequency discharge of gas is mounted with an electronic device to be processed, and an electric cable is connected to an electric terminal part of the electronic device to be processed, and at least the electric cable is connected. One conductor is electrically connected to the target electrode, the electric cable is connected to a measuring device for measuring characteristics of the processed electronic element, and the measurement is performed from the processed electronic element of the electric cable. Bending to form an inductance element on the way to the vessel, and having a reactance component for the high frequency for discharge between the target electrode and the measuring instrument, the characteristics of the processed electronic element in the measuring instrument A method of trimming an electronic element by sputter etching, wherein the element to be processed is trimmed by sputter etching while monitoring.