JPH0226023A - Monitor of discharge for plasma treatment - Google Patents

Abstract

PURPOSE:To detect an abnormal discharge in an early stage by a method wherein the electrode voltage of a plasma treatment apparatus is taken out and the application duration time of a discharge voltage, frequency of the abnormal voltage generation and various voltage data are detected and displayed from envelope components of a radio frequency voltage. CONSTITUTION:A radio frequency voltage appearing at the electrode 104a of a plasma treatment apparatus 1 is taken out by a radio frequency voltage detector 2 and the radio frequency voltage is regulated so as to be at a voltage level at which the voltage is easily subjected to a signal treatment. The envelopes VP+ and VP- of the radio frequency voltage are taken out by an envelope detecting parts 4 and the status of the discharge is monitored with the signals. In other words, the duration time of a plasma is measured, generation of an abnormal voltage is detected and counted and the peak of the electrode voltage, the peak voltage and the cathode drop voltage of the plasma treatment apparatus are measured and obtained data are displayed and processed. With this constitution, all the variations of the plasma status and the abnormal discharges are quantitatively monitored and warnings of highly harmful influences upon the plasma treatment apparatus and production of defective semiconductor devices can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to plasma processing technology, particularly for reducing the adverse effects of unstable plasma discharge on semiconductor devices and plasma processing equipment. The present invention relates to a discharge state monitoring device for plasma processing, which is effective for early detection of process defects.

[Conventional technology]

One of the major issues facing plasma processing equipment is maintaining stable operation of the equipment over a long period of time. If the stability of the apparatus is disrupted, abnormal discharge occurs when the plasma state changes during plasma processing. These factors greatly contribute to damage to processing chambers and mass production of semiconductor devices with incomplete plasma processing, and are a major cause of reduction in yield and throughput in semiconductor manufacturing processes.

One way to compensate for changes in the plasma state is to install an observation window in the processing chamber so that workers can observe the inside of the plasma processing chamber. However, due to the structure of plasma processing equipment, observation is often insufficient, and it has not been possible to accurately compensate for changes in the plasma state. In addition, plasma discharge has unique characteristics for each device, and each device must have one observer, which is practically difficult. For example, JP-A No. 5
There is a publication No. 9-41475. This consists of a plasma processing device that includes: ■ a single or double probe that detects plasma potential, ■ a photosensor that detects plasma light through a viewing window, ■ a cathode drop voltage detector that detects the DC component of the discharge applied voltage. A discharge detection device is provided, the detected signals are compared with a predetermined setting value, the discharge state is determined, and the trigger power source is controlled based on the result to automate the plasma processing apparatus.

This method is an excellent method because it allows the examination of plasma potential, plasma light, cathode drop voltage, and discharge state from various aspects. However, this method requires the installation of various detectors in each part of the plasma processing apparatus, making it difficult to simply attach it to an existing plasma processing apparatus.

Other known techniques for automatically monitoring or suppressing abnormal discharge include, for example, as disclosed in Japanese Unexamined Patent Publication No. 57-174465, which monitors the DC bias voltage VDO generated at the electrode and adjusts it to a predetermined optimum VDO. There were devices that controlled the pressure inside the processing chamber.

This method is excellent for detecting abnormal discharges caused by gradual changes in the DC bias voltage VDO, but because it uses an inductance in the monitor device, it is Abnormal discharge and DC bias voltage due to changes in vn.

It is not possible to detect abnormal discharges that do not show any change.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the installation method for installing in an off-the-shelf plasma processing apparatus, the detection of a device in which the cathode drop voltage changes abruptly, or a change in the plasma state in which no change appears in the cathode drop voltage. There wasn't. Also,
Plasma potential and cathode drop voltage vary greatly depending on the plasma processing equipment and process conditions, and the part that detects the voltage must be equipped with a means to deal with it, but in the past, this has not been fully considered.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, to quantitatively grasp all plasma state changes and abnormal discharges, and to catch signs of υ that have a large negative impact on plasma processing equipment and the production of defective semiconductor devices. An object of the present invention is to provide a discharge state monitoring device for plasma processing that can perform the following tasks.

[Means to solve the problem]

In order to solve the above problem, various parameters of the plasma processing apparatus were measured when plasma discharge was unstable.

As a result, it was found that the electrode voltage of the plasma processing apparatus shows a significant change when the plasma discharge is unstable compared to when a stable plasma discharge is obtained. Therefore,
A detailed measurement of the electrode voltage reveals that during stable discharge, a high-frequency voltage with a constant amplitude and a certain period is applied to the electrode of the plasma processing equipment, but when an abnormality occurs in the plasma discharge, , ■ The duration of voltage generation, that is, the duration of plasma discharge, varies greatly; ■ Sharp fluctuations occur in the electrode voltage envelope; ■ Peak-to-peak voltage of the electrode voltage and cathode drop voltage (DC component in high-frequency voltage) ) was found to be unstable.

The above objective can be achieved by automatically and accurately evaluating the state of plasma discharge, so it is effective to automatically and accurately monitor the state of change in electrode voltage as mentioned in ■■■. . Therefore, we extracted the electrode voltage of the plasma processing equipment without being affected by the voltage level specific to the plasma processing equipment, and from the envelope component of the extracted high-frequency voltage, we determined the application duration of the discharge voltage, the frequency of occurrence of abnormal voltage, and various voltage data. The configuration is such that it is detected and displayed. Further, by processing each detected data, it is possible to accurately and quantitatively evaluate the state of plasma discharge.

[Effect]

The discharge state monitoring device for plasma processing of the present invention uses a high frequency voltage detector to extract the high frequency voltage generated in the electrode section of the plasma processing device, adjusts the obtained high frequency voltage to a voltage level that is easy to process the signal, and detects the envelope. The envelope of the high-frequency voltage is extracted at the section, and the discharge state is monitored using this envelope signal. Monitoring consists of: ■ Measuring the duration of plasma discharge with the discharge duration measuring section in the discharge condition monitoring device; ■ Detecting and counting the occurrence of abnormal voltage with the abnormal voltage detection section; ■ Using the voltage measuring section to measure the duration of plasma discharge The peak-to-peak voltage and the cathode drop voltage are measured, and the obtained data is displayed on the display and then processed by the arithmetic processing section via the interface section.

Since the electrode voltage of a plasma processing apparatus well represents the discharge state, it is possible to accurately understand the discharge state by examining the electrode voltage from various aspects. This will be explained using FIGS.

The configuration of a typical plasma processing apparatus is also shown in FIG. 1, which shows Example 1.

The plasma processing apparatus 1 includes a power supply device and a plasma generation device.

The power supply device amplifies high frequency power obtained from a power supply 101 with a power amplifier 102, and supplies the necessary power to the plasma generation device via a matching box 103 that matches the plasma generation device.

The plasma generator is a part called a processing chamber. The inside of the processing chamber 104 includes an electrode 104a for applying electric power and an electrode 104b for placing the plasma-treated object 105, and is always maintained at a constant atmosphere by an exhaust device and a gas supply device (not shown).

<Example 1> Example 1 of the present invention will be described. The configuration of the device is as shown in FIG. an attenuator 3 that attenuates the voltage level of the obtained high-frequency voltage; an envelope detection section 4 that extracts the envelope V, + VP- of the high-frequency voltage attenuated by the attenuator 3; A discharge duration measuring section 5 that measures the duration of the voltage envelope, that is, the duration of plasma discharge, a discharge duration indicator 8 that displays the measurement result of the discharge duration, and a high frequency detected by the envelope detection section 4. an abnormal voltage detection unit 6 that detects and counts the occurrence of a steep fluctuation in the voltage envelope; an abnormal voltage occurrence frequency display 9 that displays the number of abnormal voltage occurrences counted by the abnormal voltage detection unit 6; A voltage data processing unit 7 measures various voltage values applied to the electrode 104a of the plasma processing apparatus 1 from the envelope signals V, +, and VP− detected by the envelope detection unit 4, and a voltage data processing unit 7 that measures the measured voltage data. a voltage data display device 1o for display; an interface unit 11 for importing discharge duration data, abnormal voltage occurrence frequency data, and voltage data obtained by the components mentioned above into an arithmetic processing unit; It is comprised of an arithmetic processing unit 12 that evaluates the state of plasma discharge by monitoring variations and trends in each piece of data that has been imported.

Next, the operation of the plasma processing discharge monitoring device configured as described above will be explained.

The electrode 104a of the plasma processing apparatus 1 has a processing chamber 104.
A voltage is generated by applying power to the

An example of the voltage extracted by the high frequency voltage detector 2 and attenuator 3 is the waveform shown in FIG. Among these waveforms, the following are the ones that best represent the state of plasma discharge: (1) duration of plasma discharge, (21 occurrence of abnormal voltage), (3) peak-to-peak voltage, cathode drop voltage (included in high-frequency voltage) DC component).

(1) Method for Measuring Discharge Continuation Time An example of the configuration of the discharge continuation time measuring section 5 is shown in FIG. 4, and operation waveforms of each part are shown in FIG. 5, and the discharge continuation time measurement operation will be explained.

The peak-to-peak voltage VPP (FIG. 5 (1)) of the high frequency voltage is obtained from the envelope signal vP+, V, - obtained by the envelope detection section 4 by the 1:1 inverter 501 and adder 502. . A comparator 5 having a comparison voltage setting device 504
03, and the presence or absence of discharge is determined as shown in FIG. 5 (it). Here, the clock 506 is enabled by the gate 506 only during the discharge cloth, and the discharge continuation time is measured by the timer counter 507 (FIG. 5). buffer 5
08 is used to drive the discharge duration indicator 8.

(2) Detection and counting method of abnormal voltage generation An example of the configuration of the abnormal voltage detection section 6 is shown in FIG. 6, and operation waveforms of each part are shown in FIG. 7, and abnormal voltage detection and counting operations will be explained. The description here will be omitted because only the variation detection of the envelope signal vP+ is performed, but the variation detection on the vP- side can be similarly performed.

From the envelope signal vP+ obtained by the envelope detection section 4, only its variation is extracted by a high-pass filter 602 (FIG. 7 (II)) and input to an amplifier 605.

The amplification factor of the amplifier 603 is set to the peak-to-peak voltage VPP by the low-pass filter 601 and automatic gain setter 604.
is inversely proportional to the size of (Figure 7 (ll
+1). The output of this amplifier 605 is set to a threshold value (Vth■
) setter 605, L*I value (Vth (ri) input to comparator 607 with setter 6o6 (Fig. 7
1v)) Therefore, it is possible to always detect an abnormal voltage at a constant ratio to the magnitude of the peak-to-peak voltage VPP. (In other words, the abnormal voltages of ■ and ■ in Fig. 7 (1)) have the same magnitude Δ
V, but the peak-to-peak voltage VPP is larger in ■. The abnormal voltage (2) generated in (2) is much smaller than the magnitude of VPP and has little effect on the equipment and plasma processing, so there is no need to detect it. ) The detection signal obtained in this way (Fig. 7 (■)) is OR
The signal is inputted to a counter 609 via a gate 608, and the number of occurrences of abnormal voltage is counted. The buffer 610 is used to drive the abnormal voltage occurrence count display 9.

(31 [Pressure measurement method The voltage to be measured is: l) Peak-to-peak voltage vPP, cathode drop voltage VDO%, which varies sequentially during discharge. l) Maximum value of vT'P and vDO during discharge, VPP (?7LcLs),
Vno (WL8g), 111) vPP (7""t) + vDo (P"nt) after a certain period of time from the start of discharge.The voltage data of these l), II), l11) is the envelope signal vP+, It is obtained by processing vP- in hardware in the voltage data processing section 7.

An example of the configuration of the voltage data processing section 7 is shown in FIG. 8, and its operation will be explained below.

First, from the envelope signal vP+vP- obtained by the envelope detection section 4, the adder 801 in the voltage data processing section 8 generates the cathode drop voltage vno by the 1/2 multiplier 802, and the peak voltage is determined by the inverter 808 and the adder 809. -Create peak voltage vPP.

Adder 801.172 vDo obtained from multiplier 802 is A/
A D converter 805 converts the analog-to-digital signal and outputs it. Analog-to-digital conversion is performed by clock generator 8
04 clock is sequential. By making this clock more detailed, it is possible to know the fluctuation status of vDo.

Cathode drop voltage VDO (pai
nt ) is obtained by holding the vDO value obtained by the A/D converter 805 in the holding circuit 805. The hold signal can be generated by a hold signal generator (not shown) that generates the hold signal after a certain period of time from the start of discharge.

The maximum value VDO (mαX) of the cathode drop voltage is obtained by inputting "Do" obtained by the A/D converter 803 to the A side of the digital comparator 806, and calculating the maximum value before that data (B side of the digital comparator 806). If A>B, the new value is obtained by holding the maximum value holding circuit 807.

Peak-to-peak voltage (Vpp, vppCpaint)
, VppCmar) can be obtained in the same manner, so their explanation will be omitted here.@ With the operations described above, the discharge duration of the plasma discharge, the detection of the occurrence of abnormal voltage, and the measurement of various voltage data are performed. These measured values are displayed on the displays 8 to 10 and are also taken into the arithmetic processing section 12 via the interface section 11. Arithmetic processing'! [In h12, the state of plasma discharge is quantitatively evaluated by monitoring the variations and trends in each value of the captured data.

<Example 2> Example 2 of the present invention will be described. As shown in FIG. 2, the configuration of the apparatus includes a high-frequency voltage detector 2 that extracts the voltage generated by applying power to the electrode 104a of the plasma processing chamber 1, and a an attenuator 3 that attenuates the voltage level of the high frequency voltage attenuated by the attenuator 3; an amplifier 15 that secures a voltage level so that the high frequency voltage attenuated by the attenuator 3 can be easily processed in subsequent stages; and an amplifier 13 that outputs the high frequency voltage. Envelope of high frequency voltage vP+・v,−
The envelope detection section 4 which outputs
A discharge duration measuring section 5 measures the duration of the envelope of the high frequency voltage obtained by the amplifier 14, 15 and the envelope detection section 4, which always maintains a 1/A relationship, that is, the duration of the plasma discharge, and the discharge duration measuring section 5 measures the duration of the plasma discharge. A discharge duration indicator 8 that displays the time measurement result, an abnormal voltage detection unit 6 that detects and counts the occurrence of a steep fluctuation in the envelope of the high-frequency voltage detected by the envelope detection unit 4, and .

An abnormal voltage occurrence count display 9 that displays the number of occurrences of abnormal voltage counted by the normal voltage detection section 6, and an envelope signal V, +V, - detected by the envelope detection section 4 from the plasma processing apparatus 1 The voltage data processing unit 7 that measures various voltage values applied to the electrode 104a, the voltage data display 10 that displays the measured voltage data, and the discharge duration obtained by the components mentioned above. An interface unit 11 for inputting data, data on the number of abnormal voltage occurrences, and voltage data to the arithmetic processing unit, and an arithmetic processing unit 12 for evaluating the state of plasma discharge by monitoring the variations and trends of each input data. It is configured.

Next, the operation of the discharge monitoring device for plasma processing configured as described above will be explained.

The difference from the first embodiment is that an amplifier 15 and amplifiers 14 and 15 that always maintain a relationship of 1A with the amplification factor A of the amplifier 13 are added.

The voltage applied to the electrodes of the plasma processing apparatus 1 varies considerably depending on the food of the plasma processing apparatus and the atmosphere of the plasma processing chamber. However, since the attenuator 3 can only attenuate the voltage at a constant rate, if an unpredicted voltage is generated at the electrode, the envelope detector 4 detects the correct envelope V.
There was a risk that +, V, and - could not be obtained and that the attenuator 5 itself would be destroyed.

Therefore, the attenuation rate of attenuator 3 should be increased (for example, 60 d
B), and the amplifier 13 detects the envelope detection section 4.
Amplify the voltage signal to a voltage level that is easy to process with
, +, V, - are obtained. But this vP-? .

Since the vP- signal is amplified by an arbitrary amplification factor AK in the amplifier 13, if this -it is inputted to the voltage data processing section 7, a voltage value measurement error will occur. So amplifier 1
Amplifier 14.15 that always maintains a relationship of 1A with the amplification factor A of 3
Perform the operation to return the output level to the same level as the output level of attenuator 3.

After this, operations and processes similar to those described in Example 1 are performed, and the discharge duration of plasma discharge, detection of abnormal voltage, and measurement of various voltage values are performed. These measured values are displayed on the display 8~
The value is displayed on the screen 10 and is also input into the arithmetic processing section 12 via the interface section 11. Arithmetic processing unit 1
In step 2, variations and trends in each value of the captured data are monitored to quantitatively and accurately evaluate the state of plasma discharge.

〔Effect of the invention〕

The present invention has an excellent installation method for installing in a ready-made plasma processing apparatus, and is capable of detecting a case where the cathode drop voltage changes abruptly or a change in the plasma state in which no change appears in the cathode drop voltage. Since it is equipped with means that can respond to voltage levels that vary greatly depending on the process conditions, plasma Regardless of the type of processing device, it can be obtained correctly, and by monitoring the electrode voltage during discharge with this device, it is possible to catch signs of these situations occurring and take countermeasures in advance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing a second embodiment of the present invention, and FIG. 3 is a diagram showing high frequency waves generated in the electrode section of a plasma processing apparatus during plasma processing. Figure 4 is a diagram showing an example of the voltage, Figure 4 is a diagram showing an example of the configuration of the discharge duration measuring section, Figure 5 is a diagram showing the waveforms of each main part in Figure 4, and Figure 6 is the diagram of the abnormal voltage detection section. FIG. 7 is a diagram showing waveforms of each main part in FIG. 6, and FIG. 8 is a diagram showing an example of the configuration of the voltage data processing section. DESCRIPTION OF SYMBOLS 1... Plasma processing apparatus, 2... High frequency voltage detector, 6... Attenuator, 4... Envelope detection part, 5...
Discharge duration measuring section, 6... Abnormal voltage detection section, 7...
・Voltage data processing unit, 8...Discharge disconnection time indicator, 9
... Abnormal voltage occurrence frequency display, 10... Voltage data display, 11... Interface section, 12... Arithmetic processing section. 〉 Compiled diagram

Claims (1)

[Claims] 1. In a plasma processing apparatus equipped with a plasma generating means and a high frequency power applying means for applying high frequency power to the plasma generating means, a high frequency voltage component for detecting a high frequency voltage component applied by the high frequency power applying means. A voltage detection means, an envelope detection means for detecting an envelope of the high frequency voltage detected by the high frequency voltage detection means, and a duration time of plasma processing is measured based on a signal obtained by the envelope detection means. A discharge duration measuring means, an abnormal voltage detection and counting means for detecting and measuring the occurrence of an abnormal voltage based on the signal obtained by the envelope detection means, and a signal obtained by the envelope detection means. A voltage measuring means for measuring the discharge voltage during plasma discharge, and an arithmetic processing means for evaluating the plasma processing based on various data obtained from the discharge duration measuring means, the abnormal voltage detection and counting means, and the voltage measuring means. A discharge state monitoring device for plasma processing characterized by comprising: 2. An amplifying means for amplifying the high frequency voltage detected by the high frequency voltage detecting means is provided between the high frequency voltage detecting means and the envelope detecting means, and the output of the envelope detecting means is further attenuated to reduce the discharge. 2. The discharge state monitoring device for plasma processing according to claim 1, further comprising attenuating means for inputting the voltage to the duration measuring means, the abnormal voltage detection and counting means, and the voltage measuring means.