JP2002033310A - Plasma treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment equipment, by which the yield of a semiconductor device is enhanced and surface treatment, having high accuracy, is enabled by rapidly detecting the generation of charging damage. SOLUTION: In the plasma treatment equipment, composed of a plasma- generating means for generating plasma in a treatment chamber, the treatment chamber, to which an evacuation device is connected and the inside of which can be decompressed, a gas feeder into the treatment chamber, a substrate electrode on which a material to be treated is placed, and a high-frequency power supply connected to the substrate electrode, the plasma treatment equipment is constituted, so as to have a function of detecting higher harmonics from a quinary harmonic to an octenary harmonic of an electrode current. When the higher harmonic components from the quinary harmonic to the octenary harmonic of the electrode current reach a preset value or larger, an etching treatment having high accuracy in low damage is enabled, and the effect where the yield of the semiconductor device can be improved is displayed, because the generation of charging damage can be prevented by controlling the equipment, to stop the working of the equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus suitable for etching a sample such as a semiconductor element substrate by plasma.

[0002]

2. Description of the Related Art As described in, for example, "Charging Damage in Semiconductor Process" edited by Moritaka Nakamura and Realize Inc., 1996, a conventional plasma processing apparatus has a potential distribution on a material to be processed due to unevenness in plasma. Is formed, and charging damage that deteriorates the withstand voltage of the gate oxide film may occur. Charging damage is usually evaluated using a TEG wafer, but TEG wafer analysis cannot be performed in real time, and there is no means to detect the occurrence of charging damage in real time when performing plasma processing on a workpiece. there were.

[0003]

As the degree of integration of a semiconductor integrated circuit increases, for example, the gate oxide film of a MOS (Metal Oxide Semiconductor) transistor, which is a typical example of a semiconductor device, becomes thinner, and the gate oxide film becomes damaged due to charging damage. The problem of dielectric breakdown of the film is becoming more serious. An object of the present invention is to provide a plasma processing apparatus capable of increasing the yield of semiconductor devices and rapidly performing surface treatment by quickly detecting occurrence of charging damage.

[0004]

In order to achieve the above object, the fifth to eighth harmonics of the current flowing through the wafer mounting electrode are detected. As the fifth to eighth harmonic components of the electrode current are larger, charging damage is more likely to occur. Therefore, when the fifth to eighth harmonic components of the electrode current exceed a certain set value, the operation of the apparatus is controlled to be stopped, thereby preventing the occurrence of charging damage and preventing the semiconductor device from being damaged. The yield can be improved.

[0005]

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of an etching apparatus which is an embodiment of a plasma processing apparatus to which the present invention is applied. A processing vessel 104, a dielectric window 102 (for example, made of quartz), and an upper electrode 103 (for example, made of Si) are installed on the upper portion of the vacuum vessel 101 having an open top.
The processing chamber 120 is formed by sealing. The upper electrode 103 has a porous structure for flowing an etching gas, and is connected to a gas supply device 107. Further, a vacuum exhaust device (not shown) is connected to the vacuum vessel 101 via a vacuum exhaust port 106. A coaxial line 111, a matching device 110a, and a matching device 110 are provided above the upper electrode 103.
b, high-frequency power supply 10 through filters 109 and 113
8 (for example, frequency 450 MHz) and an antenna bias power supply 112 (for example, frequency 13.56 MHz). Further, the substrate electrode 1 on which the processing target material 116 can be placed
Reference numeral 15 is installed below the vacuum vessel 101 and connected to a high-frequency power supply 117 (for example, 800 kHz) via a matching unit 118. In addition, an electrostatic chuck power supply 121 is connected to the substrate electrode 115 in order to electrostatically attract the workpiece 116.

After the inside of the processing chamber 120 is depressurized by a vacuum exhaust device (not shown) in the apparatus configured as described above, an etching gas is introduced into the processing chamber 120 by the gas supply device 107 and adjusted to a desired pressure. . High-frequency power of, for example, 450 MHz oscillated from the high-frequency power supply 108 propagates through the coaxial line 111, is introduced into the processing chamber 120 through the upper electrode 103 and the dielectric window 102, and generates a magnetic field generating coil 114 (for example, a solenoid coil) A high-density plasma is generated in the processing chamber 120 by the interaction with the magnetic field formed by the process. In particular, when a magnetic field intensity (for example, 160 G) that causes electron cycloton resonance is formed in the processing chamber, high-density plasma can be efficiently generated. Further, for example, high-frequency power having a frequency of 13.56 MHz is supplied from the antenna bias power supply 112 to the upper electrode 103 via the coaxial line 111.

The workpiece 116 placed on the substrate electrode 115 is supplied with high-frequency power (for example, 800 kHz) from a high-frequency power supply 117 and subjected to surface treatment (for example, etching). Substrate electrode 1 during etching process
15, a voltage sensor 122 and a current sensor 123
And input the voltage and current data to the current / voltage detection storage circuit 129. For example, the current / voltage detection circuit 129 has the following function. The data obtained by the voltage sensor 122 and the current sensor 123
4, the signal is converted into a digital signal.
It is stored for one or more cycles of the current waveform. The digital signal is averaged by the averaging circuit 125, and the FFT circuit 126 and the arithmetic circuit 127 perform spectrum analysis, harmonic component extraction, distortion calculation, and Vdc / Vpp ratio calculation. When input to the control circuit 128, the high frequency power supply 108, the antenna bias power supply 112,
Feedback control can be performed on the high frequency power supply 117. Due to fluctuations in the output of the high-frequency power supply 117 and fluctuations in the generated plasma, feedback control can be performed with high accuracy by averaging the obtained data.

FIG. 2 shows a current waveform obtained by averaging 1024 cycles of the high-frequency power supply 117 using the above-described current-voltage detection storage circuit. The vertical axis represents the current value (A), and the horizontal axis represents time (μsec). FIG. 2A shows a current waveform when charging damage has occurred, and FIG. 2B shows a current waveform when charging damage has been suppressed. Current waveform 2 with charging damage
01 is distorted on the positive current side, whereas the current waveform 202 in which charging damage is suppressed is sinusoidal.

FIG. 3 shows an FFT circuit 126 of an electrode current waveform.
2 shows a spectrum distribution which is an output of FIG. The vertical axis is the electrode current (arbitrary unit), and the horizontal axis is the frequency. Fig. 3 shows the spectrum distribution when charging damage has occurred.
FIG. 3B shows the spectrum distribution when charging damage is suppressed. In the spectrum distribution 301 in which the charging damage has occurred, the harmonic component of the high-frequency power supply 117 is observed, whereas the spectrum distribution 30 in which the charging damage is suppressed is observed.
In No. 2, no harmonic component is observed. The arithmetic circuit 127
3 (1) is 0.20, and that of FIG. 3 (2) is 0.057, and it has been found that the distortion is clearly different depending on whether or not charging damage has occurred. The distortion rate here is defined by the following equation.

(Equation 1)

FIG. 4 shows the relationship between the gate oxide film voltage related to charging damage and the electrode current distortion factor. The vertical axis represents the voltage between gate oxide films, and the horizontal axis represents the electrode current distortion factor. As the electrode current distortion ratio increases, the voltage between gate oxide films also increases, and charging damage can occur. That is, the occurrence of charging damage can be detected by comparing the distortion rate of the electrode current waveform with a preset threshold value.

According to the present embodiment, the distortion rate of the substrate electrode current waveform during etching is calculated, and when the threshold value exceeds a preset threshold value, the operation of the apparatus is stopped to control the charging damage. Since the occurrence can be prevented beforehand, low-damage and high-accuracy etching can be performed, and the yield of semiconductor devices can be improved.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. The configuration of the device is the same as that of FIG.
FIG. 5 shows each harmonic component ratio of the electrode current obtained by the FFT circuit 126. The vertical axis represents the electrode current (arbitrary unit), and the horizontal axis represents the order of the harmonic. The harmonic component ratio when charging damage is occurring is shown at 502, and the harmonic component ratio when charging damage is suppressed is shown at 501. In the case of charging damage 502, the fifth to eighth harmonic components are large, and in the case of suppressing charging damage 501, the fifth to eighth harmonic components are suppressed.
The next higher harmonic component is smaller. As a result of investigating various cases, it has been found that the fifth to eighth harmonic components are most sensitively correlated with the occurrence of charging damage. That is, the fifth to eighth harmonic components of the electrode current waveform are calculated, and the occurrence of charging damage can be detected based on a preset threshold value. According to the present embodiment, the fifth to eighth harmonic components of the electrode current waveform are calculated, and control is performed so that the operation of the device is stopped when the value exceeds a preset threshold value, thereby preventing the occurrence of damage. Since this can be prevented beforehand, the same operation and effect as in the first embodiment can be obtained.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to FIG. The configuration of the device is the same as that of FIG. FIG. 6 shows the relationship between the gate oxide film voltage related to charging damage and the Vdc / Vpp ratio of the substrate electrode voltage. Vdc is the average value of the DC bias voltage applied to the substrate electrode 115, and Vpp is the average value of the peak-to-peak voltage of the high frequency voltage applied to the electrode.
The Vdc / Vpp ratio is a value obtained by dividing the above Vdc by Vpp, and the Vdc / Vpp ratio is calculated by the arithmetic circuit 127. The vertical axis is the voltage between gate oxide films, and the horizontal axis is Vdc / Vpp.
It can be seen that as the Vdc / Vpp ratio decreases, the voltage between the gate oxide films increases and charging damage occurs. That is, charging damage can be detected by comparing the Vdc / Vpp ratio with a preset threshold value. According to this embodiment, Vdc / Vpp of the substrate electrode voltage waveform during etching is used.
By calculating the ratio and controlling to stop the operation of the device when the ratio exceeds a preset threshold, it is possible to prevent the occurrence of charging damage beforehand,
The same operation and effect as those of the first embodiment are obtained.

As described above, in the embodiment, the operation of the apparatus is controlled to stop when the threshold value exceeds a preset threshold value.
3, the output of the high-frequency power supply 118 or the like, or the gas flow rate,
Feedback may be provided to the gas pressure to automatically suppress occurrence of charging damage, and control may be performed to enable low-damage and high-accuracy etching. Also, by storing various data during the etching process for at least one cycle of the substrate voltage / current waveform and performing an averaging process, it is possible to suppress the influence of the output fluctuation of the high-frequency power supply 117 or the fluctuation of the generated plasma, thereby achieving a stable In addition, there is an effect that highly accurate process control (APC) can be performed.

In the above embodiment, the dry etching apparatus using a magnetic UHF discharge has been described as an example. However, other discharges (cathode-coupled discharge, anode-coupled discharge, inductively-coupled discharge, magnetron discharge, Excitation discharge, transfer coupled discharge, microwave discharge, UHF
A dry etching apparatus using discharge, VHF discharge, ECR discharge, DC discharge, etc. has the same effect. In each of the above embodiments, the dry etching apparatus has been described. However, other plasma processing apparatuses, for example, a sputtering apparatus, a plasma CVD apparatus, an ashing apparatus, and a surface reforming apparatus have the same effect.

[0016]

According to the present invention, from the fifth order to the eighth order of the electrode current,
When the next harmonic component exceeds a certain set value, the operation of the device is controlled to be stopped so that the occurrence of charging damage can be prevented beforehand. It is possible to improve the yield of semiconductor devices.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an etching apparatus according to a first embodiment using the present invention.

FIG. 2 is an electrode current waveform showing a phenomenon applied to the present invention, wherein 202 is an electrode current waveform when charging damage is occurring, and 201 is an electrode current waveform when charging damage is suppressed.

FIG. 3 is a spectrum distribution showing a phenomenon applied to the present invention. 302 is when charging damage is occurring
Reference numeral 301 denotes a spectrum distribution when charging damage is suppressed.

FIG. 4 is a correlation diagram between an electrode current distortion factor and a gate oxide film voltage.

FIG. 5 shows each harmonic component ratio of an electrode current showing a phenomenon applied to the present invention. Reference numeral 502 denotes a ratio of each harmonic component of the electrode current when charging damage is occurring, and 501 denotes a ratio when the charging damage is suppressed.

FIG. 6 is a correlation diagram of a Vdc / Vpp ratio and a voltage between gate oxide films.

[Explanation of symbols]

 Reference Signs List 101 vacuum container 102 dielectric window 103 upper electrode 104 processing container 106 vacuum exhaust port 107 gas supply device 108 high frequency power supply 109 filter 110a, b matching device 111 coaxial line 112 antenna bias power supply 113 filter 114 magnetic field generating coil 115 substrate electrode 116 covered Processing material 117 High-frequency power supply 118 Matching unit 120 Processing chamber 121 Electrostatic chuck power supply 122 Voltage sensor 123 Current sensor 124 A / D converter 125 Average processing circuit 126 FFT circuit 127 Operation processing circuit 128 Control circuit 129 Current / voltage detection storage circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiichi Watanabe 794, Higashi-Toyoi, Katsumatsu-shi, Yamaguchi Pref. AA06 BA03 BA04 BA13 BA14 BA20 BB13 BD01 BD04 CA03 CB05 5F045 AA09 BB16 BB20 EH01 EH11 EH12 EH17 GB04

Claims (3)

[Claims] 1. A plasma generating means for generating plasma in a processing chamber, a processing chamber to which a vacuum exhaust device is connected and the inside of which can be depressurized, a gas supply device into the processing chamber, and a material to be processed are placed. A plasma processing apparatus comprising a substrate electrode and a high-frequency power supply connected to the substrate electrode, the plasma processing apparatus having a function of detecting fifth to eighth harmonics of an electrode current. 2. The plasma processing apparatus according to claim 1, further comprising a function of controlling an operation state of the apparatus based on fifth to eighth harmonic data of an electrode current. 3. A processing chamber to which a vacuum pumping device is connected and which can decompress the inside thereof, a gas supply device to the processing chamber, a substrate electrode on which a material to be processed is placed, and a high-frequency power supply connected to the substrate electrode A plasma processing apparatus comprising: a function of storing current waveform data or voltage waveform data of a substrate electrode for one or more cycles, and performing integration or averaging of the waveform data.