JPS62240775A - Plasma detector - Google Patents

Abstract

PURPOSE:To accurately judge the presence or absence of plasma discharge by providing a semiconductor color sensor, etc., for outputting a signal corresponding to the illuminance, etc., of plasma light received through a peephole, and discriminating whether plasma light is generated or not. CONSTITUTION:An electric field, etc., are exerted on a gaseous reactant which has been introduced into a vacuum vessel 6, and plasma is generated. The light of the plasma is irradiated on the semiconductor color sensor arranged in a circuit board 12a through the peephole 7. A signal corresponding to the luminescent color and illuminance of the irradiated light is then outputted from the sensor. The outputted signal is processed in a signal processing part, and whether the plasma is generated in the vacuum vessel 6 or not is discriminated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to plasma etching equipment and plasma CVD.
(Chemical Vapor Depositio
n) The present invention relates to plasma detection devices for various devices that utilize vacuum discharge, such as devices.

(Prior Art) Vacuum processing in which plasma is generated in a vacuum container and the plasma is used to perform etching or thin film formation is well known. When starting this vacuum processing, it is necessary to confirm that the specified plasma is generated stably, and even during the vacuum processing, it is necessary to maintain the stable state of the specified plasma so that the vacuum processing is performed normally. It is necessary to confirm.

It is inefficient for humans to check the state of plasma generation, and for this reason, plasma detection devices have been provided that automatically detect the presence or absence of plasma generation.

Figure 4 shows a conventional plasma detection device.

In Figure 0, which shows configuration examples of two types of devices (high-grade type and simple type), a pair of opposing flat electrode plates 1a and 1 are placed in a vacuum vessel (not shown) into which a reaction gas is introduced.
By applying high frequency power or DC power from a power source 2 to the pair of flat electrode plates 1a and 1b, plasma 3 is generated between the flat electrode plates 1a and 1b.

Now, as a conventional simple plasma detection device, an ammeter 4 for detecting a discharge current or a voltmeter 5 for measuring an electrode voltage that changes due to discharge is connected to the flat electrode plate 1a, and a change in the discharge current or discharge voltage is arranged. The presence or absence of plasma generation is indirectly detected.

This figure also shows a monochromator 31 (for example, H manufactured by Jobin-Ybon Co., Ltd.
2OUV type) and a photomultiplier tube 32 (
For example, there is an attached TV (Model R955 manufactured by Hamamatsu Television Co., Ltd.), and the emission spectrum is detected with high resolution (for example, 0.25 nm), and the properties of the generated plasma can be determined in detail through spectral analysis. ing.

(Measures to be Solved by the Invention) However, this conventional simple plasma detection device has the following problems.

That is, when detecting the generation of plasma using the ammeter 4, the flat electrode plates 1a and 1b may be damaged due to some reason.
There is also a problem in that energization occurs even when there is a short circuit, and the energization causes a false detection that plasma is being generated even though no plasma is being generated.

Furthermore, when detecting plasma generation using the voltmeter 5, voltage fluctuations before and after plasma generation may be extremely small depending on the pressure conditions in the vacuum container and the type of reaction gas. There is a disadvantage that discharge detection (plasma generation detection) becomes impossible.

Also, when using both the ammeter 4 and voltmeter 5 together,
Detection of plasma generation is somewhat more reliable than in the case of either alone, but the operations of the two are by no means complementary, and detection of plasma generation still suffers from considerable imperfections.

On the other hand, although high-grade plasma detection devices have the advantage of revealing all the properties of the generated plasma, they are too large and expensive, and provide too much information to be useful for daily routine work. On the contrary, it has the disadvantage of being troublesome.

The present invention has been made in order to solve the above conventional problems, and its purpose is to provide a plasma detection device that can automatically detect the presence or absence of a desired plasma reliably, clearly at a glance, and at low cost. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows. That is, the present invention includes a viewing window provided in a vacuum container that generates plasma; and a viewing window that is placed opposite to the viewing window, receives plasma light, and outputs a signal corresponding to the emission color and illuminance of the plasma light. A plasma detection device includes: a semiconductor color sensor; and a signal processing unit that processes the output signal to determine whether or not a predetermined plasma is generated.

(Function) In the present invention configured as described above, the presence or absence of plasma generation is detected as follows.

Plasma is generated by applying an electric field (or magnetic field) to a reaction gas introduced into a vacuum container by well-known means, and light from this plasma illuminates a semiconductor color sensor through a viewing window.

The semiconductor color sensor receives plasma light and outputs a signal corresponding to the emission color and illuminance of the plasma light.

By processing the output signal from this semiconductor color sensor, it is possible to determine whether or not a certain amount of plasma is generated within the vacuum container.
This allows the signal processing unit to reliably discriminate.

(Example) Hereinafter, one example of the present invention will be described based on the drawings. FIG. 1 shows the configuration of an embodiment according to the present invention.
In the figure, the vacuum container 6 is airtightly provided with a viewing window (quartz glass window) 7 through which the inside of the vacuum container 6 can be seen.
Further, a cylindrical outer box 8 is attached to the viewing window.

A board mounting part 9 protrudes from the inner wall surface of the outer box 8 facing the viewing window 7, and the board mounting part 9 is fitted with a screw 10 that is fitted into and fixed to the part 9 and a pipe 11 that is fitted into the screw 10. Multiple circuit boards (printed circuit boards) 12 using
are arranged in a hierarchical manner.

As shown in FIG. 2, a semiconductor color sensor 13 (for example, PD150 or PD151 manufactured by Sharp Corporation) is arranged on the circuit board 12a located in the viewing window 7 among the plurality of circuit boards 12. The semiconductor color sensor 13 receives the plasma light in the vacuum container 6 through the viewing window 7, and outputs a signal corresponding to the color of the plasma light, that is, a short-circuit current signal corresponding to the wavelength of the color of the plasma light. It is something. Generally, the color of plasma light differs depending on the type of reactant gas. Therefore, if the signal output from the semiconductor color sensor 13 is analyzed by the signal processing section 14, the signal output from the semiconductor color sensor 13 will be reflected in the plasma light. It is now possible to easily distinguish whether it is based on plasma light or natural light other than plasma light, and the presence or absence of plasma generation can be reliably detected.

The signal processing section 14 is formed on the circuit board 12, and the second signal processing section 14 is formed on the circuit board 12.
As shown in the figure, the signal amplification circuit 15 and the signal adjustment circuit]
6, a pair of reference power supply circuits 17 and 18, and a comparison circuit 19. The signal amplification circuit 15 inputs the output signal from the semiconductor color sensor 13 to operational amplifiers U1 and U2.
This method uses U3 to perform logarithmic compression, and then subtracts them using U3.

That is, the semiconductor color sensor 13 includes a first photodiode 23 made of a shallow PN junction, a second photodiode 2 made of a deep PN junction, and a second photodiode 23 made of a deep PN junction in one semiconductor substrate.
4 vertically (in 2R) and uses the thickness of the silicon itself as an optical filter. Therefore, both photodiodes have different spectral sensitivity characteristics, and out of the light incident on the semiconductor color sensor 13, Short-wavelength light is absorbed near the surface of silicon, and a short-circuit current 11 corresponding to the short wavelength is passed from the first photodiode 23 to the operational amplifier U.
Added to 1. Similarly, among the light incident on the semiconductor color sensor 13, long wavelength light is absorbed deep in the silicon, and a short circuit current 12 corresponding to the long wavelength is applied from the second photodiode 24 to the operational amplifier U2.

The short circuit current is logarithmically compressed and signal amplified by the logarithmic diode 25 and the operational amplifier U1.
ll signal to operational amplifier U3. Similarly, short-circuit current I2 is logarithmically compressed and signal amplified by logarithmic diode 26 and operational amplifier U2, and IogI
2 signal to operational amplifier U3.

Operational amplifier U3 uses these Iogll and logI2 signals to calculate (Iog12-1ogI +) X= (logIz/
I +) X (X is the amplification degree of operational amplifier U3)
The signal is subtracted, and the resulting value is applied to the signal adjustment circuit 16 as the output voltage ■o.

As shown in Fig. 3, the output voltage when the light is monochromatic light generally has a certain relationship with its wavelength λ, so when the light is bichromatic light such as plasma light, the output voltage Vo is the voltage due to each color light ( weighted by luminance).

The signal adjustment port &+816 is for adjusting the voltage level of the signal output from the signal amplifying circuit 15 to zero using a variable resistor VR1, and further amplifying the zero adjusted signal using an operational amplifier U4. The amplified signal is the comparison time 1.
i'819 and via line 22 to connector 20.

In this embodiment, the output signal from the semiconductor color sensor 13 is also processed by the signal processing section 14 through the line 22 and the connector provided at the cable outlet 21 of the outer box 8. The information is directly taken out to the outside and prepared for more detailed or different types of information processing.

On the other hand, the reference power supply circuits 17 and 18 apply an upper limit value and a lower limit value as comparison reference voltages to one comparison circuit. That is, as described above, a predetermined voltage signal is output from the signal amplification circuit 15 in accordance with the color of plasma light depending on the reaction gas introduced into the vacuum container 6, but the variation in the voltage value of this voltage signal is In consideration of this, an upper limit value and a lower limit value of the voltage value corresponding to the color of the plasma light are set, and the generation state of the plasma light can be determined by detecting a voltage signal that passes through this set range.

From this point of view, in this embodiment, one of the reference power supply circuits 17 and 18, for example, the voltage at the upper limit value is transferred from the reference power supply circuit 17 to the comparison circuit 19 using the variable resistor VR2.
from the other reference power supply circuit 18 to the variable resistor V
A lower limit voltage is applied to the comparator circuit 19 using R3.

One comparator circuit has operational amplifiers U5 and U6 and relay contacts. Operational amplifier U5 is signal conditioning circuit 1
The output signal value from 6 and the upper limit value from reference power supply circuit 17 are compared.

Similarly, operational amplifier U6 compares the output signal value from signal conditioning circuit 16 and the lower limit value from reference power supply circuit 18.

Then, when the output signal value is smaller than the upper limit value and larger than the lower limit value, that is, when the output signal value is within the signal passage setting range corresponding to the specified color of plasma light, the calculation is performed. A plasma detection signal is output from amplifiers U5 and U6, and this plasma detection signal is supplied via contact K from connector 20 to an external control device (not shown).

According to this embodiment having the above configuration, since the plasma light is detected by the semiconductor color sensor 13, it is almost unaffected by the strength of the discharge, and the presence or absence of predetermined plasma light emission can almost certainly be determined based on the color of the plasma. can be detected.

In addition, the discharge inside the vacuum container changes from glow discharge to LTE
(Local Thermal Equilibriu
m) Even when a transition to discharge occurs, and also when a reverse transition occurs, there is a large difference in the emission spectra between the two, so this transition can be detected immediately.

Furthermore, in this embodiment, the analog output signal from the semiconductor color sensor 3 is amplified and zero-point adjusted and is output from the signal adjustment circuit 16 via the connector 20. By monitoring the voltage value of the signal, it is also possible to get an overview of the type of gas in the vacuum container 6. Note that in the above embodiment, the signal processing section derives (10g1) and performs the corresponding processing, but I2, 1. Detection is also possible by similar processing using the sum, difference, etc.

Furthermore, it goes without saying that the semiconductor color sensor described above can be replaced with two separate photodiodes having different spectral sensitivity characteristics.

(Effects of the Invention) Since the present invention has the configuration and operation described above, it is possible to use a simple and inexpensive device and detect plasma light emission based on direct reception of plasma light. This makes it possible to extremely accurately determine whether plasma discharge is occurring normally or not.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a circuit diagram of signal processing in this embodiment, Fig. 3 is an output characteristic diagram of a signal amplification circuit, and Fig. 4 is an explanatory diagram of a conventional example. be. la, lb... flat electrode plate, 2...
Power supply, 3...Plasma, 4...Ammeter, 5...Voltmeter, 6...Vacuum container, 7...Peep window , 8...outer box,
9... Board mounting part, 1o... Screw, 11... Pipe, 12, 12a...
...Circuit board, 13...Semiconductor color sensor, 14...Signal processing unit, 15...
・Signal amplification circuit, 16... Signal adjustment circuit, 1
7.18...Reference power supply circuit, 19...
・Comparison circuit, 20... Connector, 21...
...Cable outlet, 22...Line,
23...First photodiode, 24...
...Second photodiode, 25.26...
...Logarithmic diode, 30...Discharge light, 3
1... Monochromator, 32... Photomultiplier tube, U1 to U6... Operational amplifier, V
R1~VR3...Variable resistor, K...
relay contact. Agent Patent Attorney Yoshi Hiraku Hachiman / Figure 2/Guichi Boufure Tori Takeguchi 6'' Same plot 3rd start 4th figure

Claims (1)

[Claims] A viewing window provided in a vacuum container that generates plasma;
A semiconductor color sensor is disposed facing the viewing window and receives plasma light and outputs a signal corresponding to the emission color and illuminance of the plasma light, and the output signal is processed to determine whether or not a predetermined plasma is generated. A plasma detection device comprising: a signal processing section;