JP2006286791A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus for suppressing arc discharge by preventing the plasma entrance into the gas hole of a showerhead even in case of applying a first high frequency electric power, by generating a sheath firstly with a second high frequency electric power, by adding the second high frequency electric power of 300 W to 1,000 W lower than the first frequency electric power, then adding the first frequency electric power to an upper electrode, with a time delay for 1 to 3 seconds. <P>SOLUTION: The plasma processing apparatus 10 is provided with an upper electrode 13 and a lower electrode 14 facing oppositely in a processing chamber 12. The second high frequency electric power is applied first to the upper electrode 13, and then with a time delay for 1 to 3 seconds after that, the first high frequency electric power is superimposed and applied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus for performing an etching process on a substrate to be processed, and more particularly to a parallel plate type plasma processing apparatus.

  In a manufacturing process of a semiconductor device, a flat panel display (FPD) or the like, a parallel plate type plasma processing apparatus is used to perform an etching process on a substrate to be processed such as a semiconductor wafer or a glass substrate (LCD substrate).

  As shown in FIG. 5, this type of parallel plate type plasma processing apparatus has a processing chamber 102 of an etching apparatus 100 having a conductive and airtight processing container 104 (inner dimensions of the processing container, width direction: 2,890 mm, (Longitudinal direction: 3,100 mm, height: 600 mm), and in the processing chamber 102, an upper electrode (first electrode) 106 and a lower electrode (second electrode) 108 having a gas shower head are formed. Opposed to each other. The lower electrode 108 also serves as a mounting table for a substrate G to be processed having a rectangular shape in plan view, such as a glass substrate (for example, a glass substrate having an outer shape of 1,870 mm × 2,200 mm), and the upper electrode 106 and the lower electrode Each power supply system is connected to 108. Further, a processing gas is introduced into the processing chamber 102 via a gas supply path 110, and the gas in the processing chamber 102 is exhausted via an exhaust path 112.

  Here, a first high-frequency power source 114 is connected to the upper electrode 106 via a low-pass (low-pass) filter 116, a first matching unit 118, and a capacitance 120. With such a configuration, first high frequency power of 20 kW at a predetermined frequency, for example, 13.56 MHz, is applied to the upper electrode 106.

  A second high frequency power source 122 is connected to the lower electrode 108 via a second matching unit 124. With such a configuration, a lower frequency than the frequency of the first high frequency power, for example, the second high frequency power of 10 kW at 3.2 MHz is applied to the lower electrode 108.

  With such a configuration, it is possible to control the plasma according to the plasma state and process, and to perform uniform processing on the substrate G to be processed (see Patent Documents 1 and 2).

However, in such a conventional parallel plate type plasma processing apparatus, depending on the discharge conditions, arc discharge occurs in the hole of the gas shower head of the upper electrode, resulting in a short life due to damage of the upper electrode.
Japanese Patent Laid-Open No. 2001-127045 JP 2002-313898 A

  The problem to be solved by the present invention is to prevent the occurrence of abnormal discharge (arc discharge) in the hole of the gas shower head in the plasma processing apparatus.

  According to the present invention, the first electrode and the second electrode are arranged to face the processing chamber, and the high frequency power from the high frequency power source and the low frequency power from the low frequency power source are connected to the first matching circuit and the second matching circuit. In the plasma processing apparatus configured to be applied to the first electrode and the second electrode to be grounded, the low-frequency power is superimposed on the high-frequency power and applied to the plasma processing apparatus. .

  According to the plasma processing apparatus of the present invention, arc discharge has hitherto been caused by superimposing high frequency power of a frequency lower than the first high frequency power of 300 W or more and 1000 W or less on the upper electrode in addition to the first high frequency power. Under the generated discharge conditions, the sheath at the interface of the upper electrode becomes thick, and the plasma in the processing chamber is prevented from entering the hole of the gas shower head by this sheath, so that the occurrence of abnormal discharge can be prevented.

Configuration of Plasma Processing Apparatus As shown in FIG. 1 attached, a plasma processing apparatus 10 according to the present invention includes a processing vessel 11 that is conductive and hermetically maintained (inner dimensions of the processing vessel, width direction: 2,890 mm, longitudinal Direction: 3,100 mm, height: 600 mm), and a processing chamber 12 is formed in the processing container 11. And in this processing chamber 12, the mounting base which mounts the to-be-processed board | substrate G (for example, external shape: 1,870mmx2,200mm glass substrate) of rectangular shape in planar view, such as a glass substrate carried in / out, is carried out. A conductive lower electrode 14 also serving as an electrode is disposed and grounded. Further, the upper electrode 13 is disposed in parallel to the lower electrode 14 at a position facing the substrate mounting surface of the lower electrode 14, and a 13.56 MHz matching unit (first matching unit) 16 and a 3.2 MHz use are provided. A high frequency power source (hereinafter referred to as “first high frequency power source”) 15 through a matching unit (second matching unit) 18 and a high frequency power source (hereinafter referred to as “second high frequency power source”) lower than the first high frequency power source of 3.2 MHz and 3.2 MHz. Are connected to each other). Other configurations are almost the same as those of the conventional parallel plate type plasma etching apparatus.

  As described above, the plasma processing apparatus 10 (parallel plate type plasma processing apparatus) of the present invention is configured, and plasma is generated by applying the first high-frequency power and the second high-frequency power to the upper electrode 13 in a superimposed manner. Then, the substrate G to be processed is subjected to plasma etching.

Mode of Superimposing Application of High Frequency Power and Low Frequency Power to the Upper Electrode In the plasma processing apparatus 10 of the present invention shown in FIG. 1, the first high frequency power is initially superimposed on the upper electrode 13 and is lower than the first high frequency power. After applying the second high frequency power of the frequency, the sheath is first generated at the upper electrode interface by superimposing, and then when the first high frequency power is applied, the plasma generated thereby is transferred to the upper electrode interface. As far as possible, the plasma in the processing chamber 12 is prevented from entering the hole of the gas shower head by the sheath, thereby preventing the occurrence of abnormal discharge.

  Here, the frequency of the electric power superimposed on the high frequency electric power is set as follows. That is, at a low frequency at which ions in the plasma can follow the change in the electric field of the superimposed frequency, the ions are accelerated with high energy, collide with the upper electrode 13 and damage the upper electrode 13. On the other hand, if the frequency of the superimposed power is too high, the self-bias voltage becomes small, and the sheath region is thin, so that plasma enters the hole of the gas shower head and the effect of suppressing abnormal discharge cannot be obtained. End up. According to the experiment results of the present inventor, it is preferable to superimpose power having a frequency of about 2 MHz to 10 MHz. In this case, the time difference between the superimposed powers is first applied with the second high frequency power, and then the first high frequency power. In the case of adding 1 to 3 seconds.

FIG. 2 shows the result of verifying the abnormal discharge evaluation of the upper electrode in the plasma etching chamber. O ₂ conditions (vacuum degree: 300 mTorr, inter-electrode gap: 235 mm, applied power: 5 kW) in which abnormal discharge is likely to occur. The power of 23.2 MHz was superimposed at ~ 35 kW).

  FIG. 2 shows a plot of experimental results confirming the reproducibility of the occurrence of abnormal discharge in the upper electrode when RF power (high frequency power) (W) is superimposed on the horizontal axis and 3.2 MHz is superimposed on the vertical axis. In confirming the reproducibility of occurrence of each abnormal discharge, RF power was applied every 5 kW from 5 kW to 35 kW, and the presence or absence of abnormal discharge was confirmed by changing the value of the superimposed frequency power.

  First, in the confirmation of the first experiment, 1000 W was superimposed, but no abnormal discharge was observed. In confirmation of the second experiment, 500 W was superimposed, but no abnormal discharge was observed. In confirmation of the third experiment, 300 W was superimposed, but there was no abnormal discharge. Furthermore, in the confirmation of the fourth experiment, although 100 W was superimposed, no abnormal discharge was recognized.

  Here, when confirming the first to fourth experiments, the RF output (first frequency power) of the source power supply is intermittently applied in increments of 5 kW while the second high frequency power of 3.2 MHz is first applied. did. Note that when the source power supply was OFF, the second high-frequency power of only 3.2 MHz was applied. In confirmation of the fifth experiment, when the second high-frequency power was not superimposed on the first high-frequency power, abnormal discharge was observed at 10 kW. In confirmation of the sixth experiment, 500 W was superimposed, and in confirmation of the seventh experiment, 300 W was superimposed, but no abnormal discharge was observed. Furthermore, in the confirmation of the eighth experiment, when 100 W was superimposed, small-scale abnormal discharge was observed at RF outputs of 20 kW and 30 kW. This is probably due to the fact that the power of the second high frequency, which is lower than the first frequency, is small, so that the sheath becomes thin and the plasma enters the hole of the gas shower head.

  Here, at the time of confirmation of the sixth to eighth experiments, the abnormal discharge evaluation was performed by intermittently leaving the discharge traces due to abnormal discharge from the abnormal discharge occurrence state at the time of confirmation of the fifth experiment (RF The method of applying power is the same as that in the confirmation of the first to fourth experiments).

  From this upper electrode abnormal discharge evaluation value, (i) When 3.2 MHz was superimposed on 300 W to 1000 W, abnormal discharge was not generated, but generation of small-scale abnormal discharge was observed with 100 W superimposed. (Ii) Abnormal discharge occurred without 3.2 MHz superimposition.

  From this abnormal discharge rating value, it was confirmed that the superposition of the second frequency power lower than the first frequency of 300 W or more and 1000 W was preferable in order to reliably suppress the abnormal discharge of the upper electrode. Here, the order of the superposition of the first high-frequency power and the second high-frequency power requires that the first high-frequency power be applied after first applying the second high-frequency power. Also, the time difference between the application of the first high frequency power after the application of the second high frequency power is 1 to 3 seconds.

  Moreover, since the sheath becomes thick by superimposing the second high frequency power of 3.2 MHz, there is a concern that the sheath voltage (Vdc) increases and the upper electrode is sputtered more. Therefore, as shown in FIG. 3, in order to confirm the superposition effect of the second high frequency, the upper electrode sample shaving evaluation was performed.

  In this upper electrode sample scraping evaluation, a thermal oxide film wafer piece having a size of 25 mm × 25 mm was attached to the upper electrode, and the scraping amount (sputtering amount) was measured. In FIG. 3A, CENTER is the center of the upper electrode, Edge1 is the end on the opposite side of the gate, and Edge2 is the position where the wafer piece is attached to the gate-side end just below CENTER (FIG. 3). 3 (b)).

  Furthermore, when an increase in the amount of scraping (sputtering amount) of the upper electrode was confirmed, as shown in FIG. 3 (a), an increase of 10% with a low-frequency power of 500 MHz superimposed as shown in FIG. (Here, the vertical axis in FIG. 3A represents E / R: etching rate, and the horizontal axis represents Bias Power: bias output).

  From the above experimental results, in the plasma processing apparatus 10 of the present invention, the upper electrode 13 is superposed on the upper electrode 13 by superimposing the second high-frequency power (300 W or more) having a frequency lower than the first high-frequency power of 3.2 MHz. It was confirmed that the occurrence of abnormal discharge could be prevented without damaging 13.

  On the other hand, by positively generating the sheath voltage (Vdc), there is an effect of reducing deposits (attachments) generated on the surface of the upper electrode by ion sputtering. However, if the sheath voltage (Vdc) is too large, the processing chamber is consumed. Here, it was confirmed that the smaller the superimposed power of the second high frequency, the smaller the sputtering rate.

  Furthermore, as shown in FIGS. 4A to 4D, another embodiment in which the method of applying high-frequency power to the upper electrode 13 and the lower electrode 14 is changed can be configured.

  First, in the embodiment shown in FIG. 4A, the first high frequency power source 15a and the second high frequency power source 17a are connected to the upper electrode 13a to apply high frequency power, and the third high frequency power source is applied to the lower electrode 14a. A power source 20a is connected and high frequency power is applied to obtain upper and lower three frequencies. Further, in the embodiment shown in FIG. 4B, the first high frequency power supply 15b and the second high frequency power supply 17b are connected to the upper electrode 13b to apply high frequency power, and the third electrode is applied to the lower electrode 14b. The high-frequency power source 20b and the fourth high-frequency power source 21b are connected to each other to apply high-frequency power to obtain the upper and lower four frequencies.

  Further, as shown in FIGS. 4C and 4D, the upper shower heads 13c and 13d are grounded and the second high-frequency power is applied from the second high-frequency power sources 17c and 17d, and the lower electrode 14c is applied. , 14d may be connected to the third high-frequency power source 20c or the third and fourth high-frequency power sources 20d and 21d to apply the high-frequency power to form the plasma processing apparatus of the present invention.

  The plasma processing apparatus of the present invention can be applied not only to a plasma etching apparatus having upper and lower two frequencies, but also to various processing apparatuses such as a CVD apparatus in which it is essential to prevent abnormal discharge that damages the upper electrode.

The conceptual diagram of the plasma processing apparatus of this invention. The graph which shows upper electrode abnormal discharge evaluation with the plasma processing apparatus of this invention, and the conventional plasma processing apparatus. FIG. 3A is a graph in which the low-frequency superposition effect by the plasma processing apparatus of the present invention is verified from the sample scraping amount of the upper electrode, and FIG. 3B shows the evaluation position of the sample scraping amount of the upper electrode. FIG. 4A is a conceptual diagram illustrating an embodiment of the plasma processing apparatus of the present invention, in which FIG. 4A shows the upper and lower three frequencies, FIG. 4B shows the upper and lower four frequencies, and FIG. FIG. 4 (d) shows an example of the upper and lower three frequencies, respectively. The conceptual diagram of the conventional plasma processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasma processing apparatus 11 Processing container 12 Processing chamber 13 Upper electrode 14 Lower electrode 15 1st high frequency power supply 16 1st high frequency matching device (1st matching device)
17 Second high frequency power supply 18 Second high frequency matching device (second matching device)
20 Third high-frequency power source 21 Fourth high-frequency power source G Substrate

Claims (13)

A first electrode and a second electrode are arranged opposite to the processing chamber, and a first high-frequency power from a high-frequency power source and a second high-frequency power from a high-frequency power source having a frequency lower than the first high-frequency power are In the plasma processing apparatus configured to be applied to the first electrode through the first matching circuit and the second matching circuit and to ground the second electrode,
The plasma processing apparatus, wherein the second high-frequency power is superimposed on the first high-frequency power and applied.   The plasma processing apparatus according to claim 1, wherein the first high-frequency power is applied in a state where the second high-frequency power is first applied.   The plasma processing apparatus according to claim 1, wherein a frequency of the second high-frequency power to be superimposed is in a range of 2 MHz to 10 MHz.   The plasma processing apparatus according to claim 1, wherein a frequency of the first high-frequency power to be applied is 13.56 MHz.   The plasma processing apparatus according to claim 1, wherein the second high frequency power to be superimposed is 300 W or more and 1000 W or less.   The plasma processing apparatus according to claim 1, wherein the first electrode is an upper electrode, and the second electrode is a lower electrode.   The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is a parallel plate type plasma processing apparatus. A first electrode and a second electrode are arranged opposite to the processing chamber, and a first high-frequency power from a high-frequency power source and a second high-frequency power from a high-frequency power source having a frequency lower than the first high-frequency power are In a method of applying a plasma treatment to a substrate to be processed, which is applied to the first electrode through a first matching circuit and a second matching circuit, and the second electrode is grounded and placed on the second electrode.
Applying the second high frequency power to the first electrode first;
Then, with the second high frequency power applied to the first electrode,
Applying the first high frequency power to the first electrode;
And a plasma processing method.   The plasma processing method according to claim 8, wherein the frequency of the second high-frequency power to be superimposed is in the range of 2 MHz to 10 MHz.   The plasma processing method according to claim 8, wherein a frequency of the first high frequency power to be applied is 13.56 MHz.   The plasma processing method according to claim 8, wherein the second high-frequency power to be superimposed is 300 W or more and 1000 W or less.   9. The plasma processing method according to claim 8, wherein the time difference to be superimposed is 1 second to 3 seconds. A first electrode and a second electrode are arranged opposite to the processing chamber, and a first high-frequency power from a high-frequency power source and a second high-frequency power from a high-frequency power source having a frequency lower than the first high-frequency power are In a method of applying a plasma treatment to a substrate to be processed, which is applied to the first electrode through a first matching circuit and a second matching circuit, and the second electrode is grounded and placed on the second electrode.
Applying the second high frequency power to the first electrode first;
Then, with the second high frequency power applied to the first electrode,
A computer storage medium including software for controlling to apply the first high-frequency power to the first electrode with a time difference.

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