KR20050027668A - Diagnosis system and method for measuring pulsed plasma characteristics variable - Google Patents

Abstract

The present invention is a device used to measure the current (I) -voltage (V) curve required to obtain plasma characteristic variables in a vacuum chamber, and more particularly, the time-dependent operation of the plasma in the vacuum plasma in a time-varying pulsed plasma. The key point is the device and measurement method configured using LabVIEW to get the parameters. In the present invention, a DC voltage synchronized with a pulsed plasma generated instead of a sawtooth or sinusoidal voltage used to obtain a current-voltage curve in a conventional continuous plasma is sequentially applied to a Langmuir probe. By measuring the current afterwards, a current-voltage curve over each time can be obtained.

Description

DIAGNOSIS SYSTEM AND METHOD FOR MEASURING PULSED PLASMA CHARACTERISTICS VARIABLE}

The present invention relates to an apparatus and a measuring method for measuring the characteristic variables of a newly introduced pulsed plasma instead of the conventional continuous plasma used in the surface modification of materials or the manufacture of semiconductor devices.

Plasma equipment is widely used to deposit thin films on wafers or to etch wafers and thin films in the process of manufacturing plasma ion implantation equipment and semiconductor devices for surface modification of materials. In order to effectively perform these processes, it is necessary to know the plasma potential (Vp), electron temperature (Te), electron density (Ne), ion density (Ni), etc. in the plasma. Acquisition through a Langmuir probe is the most common method.

1 is a current-voltage characteristic curve obtained by a conventional sawtooth voltage in a continuous plasma. As shown in FIG. 1, the electron current and the ion current become saturated at a constant voltage, and the plasma potential, the electron temperature, the electron density, the ion density, and the like can be obtained using the voltage and current at this time. However, as shown in FIG. 2, in the conventional method of applying a time-induced sawtooth wave in a time-varying pulsed plasma, a distorted current-voltage curve can be obtained and also plasma characteristic parameters can be obtained over time. none.

The method of obtaining a current-voltage curve by applying a DC voltage to a Langmuir probe in a pulsed plasma and measuring current (V. Kaeppelin, 2002, Plasma Source Sci. Technol., 11, 53-56) The ability to measure current is a new way to obtain current-voltage characteristic curves at each time.

However, these methods require a lot of time to obtain a single current-voltage curve, since at least 100 values between -100V and + 100V must be manually manipulated and applied to the probe before measuring the current for each voltage. Since DC voltage is not synchronized with pulsed plasma, each data is not always obtained at the same time.

Accordingly, the present invention is designed to solve the problems of the existing technology, and the object of the present invention is to form an automation of a measurement system using a data acquisition board and a lab, to obtain a more accurate current-voltage curve in a short time.

Hereinafter, with reference to the accompanying drawings to achieve the above technical problem will be described in detail.

3 shows a schematic diagram of a pulsed plasma characteristic variable measuring system according to the present invention, by synchronizing a pulsed RF power device 4 with a data acquisition board 7 and a current-voltage curve measuring system 6. An antenna (2) located within the pulse generator (8), which makes it move at the same time, and a vacuum chamber (1) for generating a pulsed plasma, which emits RF pulses, and a matching which electrically matches the antenna and the pulsed RF power device It consists of a network 3 and a Langmuir probe 5 to which a direct current voltage is applied.

The current-voltage curve measurement system includes an amplifier circuit that amplifies the voltage between -10V and + 10V from the data measurement board and applies a voltage between -100V and + 100V to the Langmuir probe.

The data analysis system consists of a data acquisition board (National Instruments Corporation, USA) that converts analog and digital signals, and a LabVIEW (National Instruments Corporation, USA) program that stores and analyzes the acquired data. It may be.

In the data analysis system, the data sampling rate is 10 kS to 250 kS / s, so that the time interval for analyzing the data can be 100 to 4 ms.

As described above, the present invention has an advantage that a current-voltage characteristic curve for obtaining characteristic variables of pulsed plasma can be obtained in a short time within several tens of seconds using a data acquisition board and a labview.

In addition, the current-voltage characteristic curve can be obtained not only in pulsed plasma but also in continuous plasma by using the method of the present invention.

(Example)

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention described above in more detail.

In order to obtain the data using the apparatus according to the present invention, the pressure in the vacuum chamber was set to 1 mTorr of argon, and a pulsed plasma was generated by applying pulse RF power 1 kW, pulse width 1 ms, and pulse frequency 100 Hz to the antenna in the vacuum chamber. The data was obtained after the position was located in the center of the vacuum chamber.

4 is a current and voltage curve with time obtained by the present invention. The principle of the method of obtaining the current-voltage characteristic curve of the pulsed plasma according to the present invention is as follows.

That is, after a pulse having a constant period is generated in the pulse generator 8, the pulse-powered power supply 4 and the timer of the data acquisition board 7 are used to operate the current-voltage curve measuring system 6. Synchronize More than 500 digital voltages from -10V to + 10V produced by the data acquisition board are converted from analog-to-analog converters (DACs) to analog voltages, and the DC voltages are then converted into amplifiers in the current-voltage curve measurement system (6). Amplified to a value between -100V and + 100V to be applied to the Langmuir probe, and then the current flowing into the probe and the actual voltage applied to the probe can be measured and stored in the computer through an analog-to-digital converter (ADC). As shown in Figure 4, we can obtain the voltage and current curves over time.

Since all the above processes are synchronized with the pulse generator, data input and output are simultaneously performed at the point of time when the pulse plasma is generated.

Then, when the data of the voltage and current at a certain time from the voltage and current curves obtained as shown in Figure 4 to extract all data through the LabVIEW to create a single data, the conventional method in the continuous plasma shown in FIG. Like the obtained current-voltage curve, a curve having a shape without distortion can be obtained, unlike in FIG. 2, even in a pulsed plasma. At this time, the voltage and the current need more than 500 to obtain a more accurate current-voltage characteristic curve.

 FIG. 5 is a current-voltage characteristic curve obtained by extracting voltage and current according to time after generating a pulse plasma from the data of FIG. 4 by using LabVIEW, and when such a curve is obtained at each time, the pulse plasma potential, electron temperature, and electron Characteristic parameters of the plasma can be obtained at each time, such as density.

FIG. 6 shows electron temperatures and electron densities obtained from current-voltage characteristic curves obtained at respective times as shown in FIG. 5. As can be seen from FIG. 6, the electron temperature and the electron density are maintained at a constant value after 500 mV and gradually decrease at the 1000 mV point at which the pulse ends. In this way, the plasma can be measured with time from the start of the pulse.

FIG. 7 is an initial screen of a lab program for pulse plasma measurement appearing on a PC monitor, and is configured to control a measurement voltage range applied to a probe, a time to be measured, and a measurement interval through a PC.

According to the present invention, when a DC voltage synchronized with a pulsed RF power device is applied to a probe by using a data acquisition board and LabVIEW, the current is measured, unlike in the case of manually applying a voltage as in the conventional pulsed plasma measurement method. Within a short time, a more accurate current-voltage curve can be obtained than conventional methods.

1 is a current-voltage characteristic curve obtained by a conventional method in a continuous plasma.

2 is a current-voltage characteristic curve obtained by a conventional method in a pulsed plasma.

3 is a schematic diagram of a pulsed plasma characteristic variable measurement system according to the present invention;

4 shows current and voltage curves over time obtained with a device according to the invention in a pulsed plasma.

5 is a current-voltage characteristic curve obtained with a device according to the invention in a pulsed plasma.

6 is an electron density and electron temperature curve of plasma with time in a vacuum chamber.

7 is an initial screen of a lab program for pulse plasma measurement appearing on a PC monitor.

<Explanation of symbols for the main parts of the drawings>

1: vacuum chamber

2: antenna

3: Matching Network

4: pulsed RF power device (13.56MHz)

5: Langmuir probe

6: current-voltage curve measurement system

7: data acquisition board

8: external trigger pulse

9: computer

Claims (4)

In the pulse plasma characteristic variable measuring method using a Langmuir probe, (a) synchronizing the pulsed RF power device and the current-voltage curve measurement system through a pulse generator, (b) generating a DC voltage in the data analysis system; (c) amplifying the DC voltage in a current-voltage measurement system synchronized with the pulse generator, (d) measuring the current flowing into the probe after applying a DC voltage to the probe in a current-voltage curve measuring system; (e) extracting each voltage and current obtained at the same time in the data analysis system to create a current-voltage characteristic curve; Pulse plasma characteristic variable measurement method comprising a. The method of claim 1, A method of measuring pulsed plasma characteristic parameters using a counter timer on a data acquisition board for synchronizing a pulsed RF power supply with a current-voltage curve measurement system. The method of claim 1, A pulse plasma characteristic variable measurement method having a time interval of 4 ms to 100 ms to analyze data of a pulsed plasma. The method of claim 1, RF pulses generated by the pulsed RF power device has a pulse width of 10 kHz to 1000 kHz, a pulse frequency of 10 Hz to 10 kHz, pulse power of 1 kW to 100 kW.