JPS59153303A - High frequency oscillator - Google Patents

Abstract

PURPOSE:To obtain a high frequency oscillator in the technological field of plasma etching which is used for high frequency power and controls a large output power easily and accurately by utilizing a power MOSFET. CONSTITUTION:A control FETQ7 connected to an amplifier element of an oscillating circuit 1, e.g. high frequency transistors (TR) Q1, Q2 and changing the bias of said high frequency TRsQ1, Q2 by the anode voltage is provided, and an output power of the oscillating circuit 1 is controlled by various controlling DC signals impressed to the base of the FETQ7. Thus, easy, accurate and large output power control is attained and stable operation is expected. Further, the high frequency oscillator with high technical value such as prevention of a trouble of short life of the oscillation in the application of plasma etching is obtained by using MOSFETsQ3-Q6 for a power amplifier circuit 3.

Description

[Detailed description of the invention] (Application field of division 1) 4. The invention facilitates plasma etching 1';
This invention relates to a frequency oscillator for F+output 1 power.

(6 o'clock) The most important part of circuit manufacturing technology is plasma etching technology.The outline of this technology is, for example, hermetic A target to be treated with a mask of a predetermined pattern is placed on the negative electrode side of the parallel plate electrode placed in contact with the gas inside the reactor, and the introduced monomer is turned into plasma between the parallel half plate electrodes.
An organic thin film is formed on the target material, and a radio frequency source is generally used as an external source for exciting the gas into a plasma state.

The high-frequency oscillator, which is the high-frequency power source, is usually a crystal oscillation circuit. :156 Ml-fz high frequency is generated, and this is amplified using a transistor or a vacuum tube for high output power, and high output high frequency power of more than 1 hull is generated from a small output of 1.00 W. However, when constructing an oscillator for high output power as mentioned above, vacuum tubes are usually used because they perform high power amplification, but vacuum tubes have a fundamental drawback that their special mission is relatively short, and in reality In use, the vacuum tube itself must be replaced or readjusted after several thousand hours, which is a major hindrance to etching work.

On the other hand, although transistors, generally semiconductor devices for amplification, do not have the same lifespan problems as vacuum tubes, it is technically difficult to obtain high-voltage and high-output devices for high-frequency devices. It is a trench, and is unsuitable for power use because it is vulnerable to secondary surrender.

However, recently, with the advancement of MO8FET (MO8 type field effect transistor), high-performance devices for high frequency and high power have been put into practical use.
Unlike transistors, T has the advantage of not having secondary breakdown and can be manufactured for high power applications.

As mentioned at the beginning, especially in the technical field of etching using plasma, the single-frequency oscillator used must handle high frequencies of more than 10 MHz, high power of several kilowatts, and stability. Various performances are required, such as being able to generate a high-precision sine wave in this state, and being able to vary the magnitude of the output power easily and significantly, and these requirements are currently not met. MO for power that fully satisfies
A high frequency oscillator using 8FET has just been developed.

(Object of the invention) The present invention is intended to meet the above-mentioned requirements.
The object of the present invention is to provide a high frequency oscillator, particularly in the technical field of plasma etching, which can be used for high frequency and high power, and can easily and accurately control the output power to a large extent.

(Structure and operation of the invention) The present invention is applied to a high frequency oscillator comprising an oscillation circuit and a power amplification circuit, and in particular, the power amplification circuit is a high power MO8FE.
Construct an amplification stage using T.

The main part of the present invention includes a control field effect transistor (FET) which is connected to the amplification element of the oscillation circuit described above, for example, a high frequency transistor, and which allows the bias of the high frequency transistor to be varied by an anode voltage. By applying a control DC signal applied to the base of this FET, for example, the signal from a detection means that obtains a DC detection signal corresponding to the output power, or an output 1J'' variable signal from an external source that can be arbitrarily varied. It is characterized by being able to stabilize the output power using a closed loop and variable control of the output power using an open loop.

(Embodiments) Below, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, FIG. 1 is an electrical circuit diagram of a high frequency oscillator according to the present invention; Figure 2 shows the input terminal vs. output voltage characteristic diagram of the control FET in Figure 1. First, the overall configuration of the oscillator will be explained with reference to Figure 1. Figure 1 in the figure shows the oscillation circuit. , high frequency npn
A crystal oscillation circuit using the transistor Q11 Qii and the crystal oscillation IX is constructed. Transistors Q1 and C2 both have their emitters connected to 1, and crystal oscillator X connected to the base side of transistor Q1 has a value of 1:3.56.
A high frequency of MI-(z is generated. Then, it is amplified by L-transistors Q1 and C2, and the output signal is taken out from I-transistor r1, which is connected to the collector side of transistor Q2. In addition, L-transistor R2 and adjustment The variable capacitor C1 is an oscillation element connected in series with the crystal oscillator X, and has symbols R, , R2, l(3,)14.
i (5, R6, R7' and R8 are the resistances for transistor Q1 or C2 for 7 < IA, C2+ C/81 C
4+ C5 and c, , (#i) (Indicates a capacitor for insulation or coupling, and these resistors and capacitors are arbitrarily selected based on the design.

By the way, as mentioned above, the high-frequency oscillator used to generate plasma is required to have a high processing precision of the processed material, so the waveform of the high-frequency wave supplied is also required to be a stable sine wave with little distortion. For some high-frequency oscillators, it is necessary to vary the output power to a large extent. Therefore, in the present invention, a capacitor C4 is connected between the emitters of transistors Q1 and C2, and a control DC voltage, which is the output of a control FET to be described later, is applied to the emitter of transistor Q2. The output of the oscillation circuit 1 is maintained as a highly accurate sine wave, and in this state it is possible to easily and more accurately vary the magnitude of the output power. Specifically, the output of the oscillation circuit 1, that is, the capacitor C9 of the coupling river, is changed by changing the DC voltage applied to the emitter of the transistor Q2.
The output can be increased by one step from zero to the maximum value -.

Now L2, capacitor C9 is connected to input 1311 of amplifier circuit 2.
1, and this output side is connected to the power amplifier circuit 3 side.The output of the oscillation circuit 1 is amplified to a desired magnitude and supplied to the power amplifier circuit 3.

The voltage amplifying circuit 3 is an inverting quadrant T35! : MO3FE for power use with uniform characteristics using high-frequency voltage generated manually
Parallel of T Qs and 04, and same < MOSi2”ET
Q, and O6 are connected in parallel, and '1(
L force) In addition to making the 1st knee a dog, it is made to perform A13 class operation to obtain low distortion characteristics.
and r3. It obtains high frequency power that is amplified.

This output power further passes through a matching circuit 4 which is configured in a π-shape with capacitors C1o and C1□, and a coil L1, and also passes through a power detection circuit 5 to an output terminal d.

Incidentally, the above-mentioned etching reactor equipped with an auto-tuning circuit at the front stage is connected as a load to the second output terminal d.

It's a good thing, especially if you omit the explanation, it, o+ R11
and R1□ are input resistances, C13I CJ41 CJ5 and C,, CJ, coupling capacitors, T7 and °r8 (l-1, bias transformers, and each of these circuit elements is set uniquely in the design. .Capacitor C
1□, C18, and variable resistor R13 are bias adjustment circuits.

On the other hand, the power distribution detection circuit 5 is connected to the feedback amplifier circuit 6 and outputs a direct current signal SI proportional to the magnitude of the output power.
is supplied to the circuit 6, and the circuit 6 compares the DC signal with a preset reference signal to obtain a DC control signal S2 based on the deviation.

The output (J) side of the amplifier circuit 6 is connected to the base of the control FET Ω7 to supply the control signal S2.

As shown in FIG. 2, the control FET O7 has extremely excellent linearity in the input terminal (base voltage) versus output voltage (ano-1/voltage) characteristic.

The cathode of the PET O7 is directly grounded, and the anode is connected to the amplification stage of the oscillation circuit 1, ie, the emitter of the transistor Q2, via the canopling capacitor C1□. The bias of the amplification stage of the oscillation circuit 1 is made to be variable in proportion to the magnitude of the voltage at the anode. Specifically, when the voltage between the gate and cathode of the FETO 7 is increased from zero, the bias as described above is changed. The output voltage of the oscillation circuit 1 is set so that it increases proportionally from zero and can be varied with maximum care. Note that C18 indicates a capacitor.

Therefore, with the above configuration, it is possible to perform closed-loop noise control, and the output power can be always kept constant.

On the other hand, a variable output signal generation circuit 7 is connected to the feedback amplifier circuit 6, and outputs an arbitrary or programmed variable output signal S7. is supplied to the amplifier 1 circuit 6, and the voltage between the base and cathode of the FETO 7 can be varied to a desired value.As mentioned above, the output power of this type of oscillator can be stably, accurately, and easily varied in an open loop. To be able to coerce people.

Note that symbols S, C, and D are input terminals of the DC power supply.

(Effects) As is clear from the above description, the high frequency oscillator according to the present invention includes an FET connected to the amplification element of the oscillation circuit and an FET that changes the bias of the amplification element by an anode voltage. By controlling the magnitude of the output power of the oscillator using various control DC signals, it is possible to easily and accurately control the output power to a large extent, and stable operation can be expected.
By using T in the power amplification stage, it is possible to provide a high-frequency oscillator with high technical value, which can eliminate the problem of short life of oscillators in the field of plasma etching.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a high frequency oscillator according to the present invention, Fig. 2 is an electric circuit diagram of a high frequency oscillator according to the present invention;
The figure is an input voltage versus output voltage characteristic diagram of the control F E 'I' in FIG. 1. 1 is an oscillation circuit, 3 is a power amplifier circuit, Q+ + 02 is a high frequency npn) 77 transistor, Q3. Q4. Q5. Q 6
is MO8 type field effect transistor for electric υ, Ω7 is control 1
j] is a single field effect transistor. Patent applicant Tokyo Denf Chemical Co., Ltd.

Claims (1)

[Claims] (+) A control field effect transistor is provided in a high frequency oscillator including an oscillation circuit and a power amplification circuit, is connected to an amplification element of the AiJ oscillation circuit, and changes the bias of the amplification element by 1-iJ by an anode voltage. A high frequency oscillator 0(2) nil power amplifier circuit is characterized in that the magnitude of the output power of the oscillator is controlled by a control DC signal 4 applied to the base of the field effect transistor. A high-frequency oscillator according to claim 1, characterized in that it is constituted by a power field effect transistor.