JP2000269198A - Method and apparatus for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute plasma treatment at a high speed and with accuracy. SOLUTION: An upper electrode 2 and a lower electrode 3 disposed counterposed inside of a plasma treatment vessel 1, a first high-frequency power source 7 supplying the lower electrode 3 with the power having an output waveform of a low-frequency component which has positive and negative cycles and a second high-frequency power source 8 supplying the lower electrode 3 with power having the output waveform of high-frequency components, are provided. The power is supplied to the lower electrode 3 with the high-frequency components of the second high-frequency power source 8 synchronized with the negative cycle of the low-frequency component of the first high-frequency power source 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and a plasma processing apparatus for performing a predetermined process on a substrate to be processed by using plasma generated by high frequency power.

[0002]

2. Description of the Related Art With the increase in the density of semiconductor devices, more sophisticated technology is required for an etching process for forming fine wiring connecting the devices. In the next generation of 1 gigabit DRAM, in order to form a via hole for connecting the upper and lower wirings by embedding a conductive material, a silicon oxide film having a diameter of 0.15 to 2 μm is formed on a silicon oxide film having a thickness of 1 to 2 μm. It is necessary to open a very fine hole diameter of 0.12 μm. When etching with such a high aspect ratio (the ratio of the thickness of the interlayer film to the hole diameter) is performed by a conventionally used parallel plate type etching apparatus, there have been various problems. One of them is a shape defect due to charging.

FIG. 5 is a schematic configuration diagram of a conventional etching apparatus. In the plasma processing vessel 1, an upper electrode 2 and a lower electrode 3 are arranged to face each other. A substrate 4 to be processed is placed on the lower electrode 3. The plasma container 1 has a gas supply system 5 for introducing a gas. This gas supply system 5
The high-frequency power generated by the high-frequency power supply 41 is supplied to the lower electrode 3 via the matching device 42 while introducing a gas from the apparatus to generate plasma in the plasma processing vessel 1.

FIG. 6 is a view for explaining an abnormal shape due to charging which occurs when the plasma processing apparatus shown in FIG. 5 is used. The substrate to be processed 4 includes a substrate 51 and this substrate 5
1 and an interlayer film 52 selectively formed on
2 comprises a resist layer 53 formed thereon. A sheath region is formed between the processing target substrate 4 and the plasma. In the sheath region, the electrons are decelerated, so that they adhere above the resist layer 53 and the interlayer film 52. Therefore, positive ions involved in the etching may be bent, making it difficult to obtain a vertical etching shape, or a phenomenon that the etching stops in the middle of the interlayer film 52 may occur.

[0005]

As described above, in the conventional etching apparatus, the positive ions involved in the etching are bent, making it difficult to obtain a vertical etching shape, or performing etching in the middle of the interlayer film. In some cases, the phenomenon of stopping occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a plasma processing method and a plasma processing apparatus which enable high-speed and highly anisotropic plasma processing. is there.

[0007]

According to a first aspect of the present invention, there is provided a plasma processing method comprising: applying a high-frequency power to at least one of an upper electrode and a lower electrode which are opposed to each other in a processing chamber; In a plasma processing method of performing a predetermined process on a substrate to be processed mounted on the lower electrode by generated plasma, at least two types of low frequency components having a positive cycle and a negative cycle and at least two types having a high frequency component Generating the high-frequency power by superimposing a frequency,
The high frequency component is applied to the electrode in synchronization with the negative cycle of the low frequency component.

According to a third aspect of the present invention, there is provided a plasma processing apparatus, comprising: a pair of electrodes disposed in a processing chamber so as to face each other; and a power having an output waveform of a low frequency component having a positive cycle and a negative cycle. A first power supply for supplying an electrode;
A second power supply for supplying power having an output waveform of a high-frequency component to the electrode, wherein a high-frequency component of the second power supply is synchronized with a negative cycle of a low-frequency component of the first power supply. An electric power is supplied to the electrode.

Preferred embodiments of the present invention will be described below.

(1) The low-frequency component of the superimposed high-frequency power is 10 kHz or more and 1 MHz or less, preferably 20 kHz.
z to 400 kHz and high frequency components of 3 MHz to 110 MHz, preferably 10 MHz to 70 M
Hz or less. More preferably, the low frequency component is 10
It is 0 kHz or less.

(2) At least two high frequency power supplies are connected to a single lower electrode.

(3) The output waveform of the high-frequency power supply applied to the electrodes is longer in the negative cycle than in the positive cycle.

(4) In the output waveform of the high-frequency power supply applied to the electrode, the period of the positive cycle is set to 50 microseconds or more.
The period of the negative cycle is 200 microseconds or more and 10 milliseconds or less.

(5) Among the outputs of the high frequency power supply applied to the electrodes, the voltage of the positive cycle is set to 50 V or more and 200 V or less.
The voltage of the negative cycle is from -500 V to -10 V.

(Operation) In the present invention, superimposed high-frequency power oscillating at different frequencies from at least two high-frequency power sources is applied to a pair of electrodes in the plasma processing vessel. The output waveform of the low-frequency component of the superimposed high-frequency power has a positive cycle and a negative cycle, and the high-frequency component is synchronized with the negative cycle and applied to the electrode. As a result, the timing at which the positive cycle of the low-frequency component is applied to the lower electrode on which the substrate to be processed is applied is secured, and the electrons efficiently enter the substrate to be processed and the negative ions generated in the plasma. Also enter the substrate to be processed at the same time. Also,
In the next negative cycle, positive ions and neutral particles suitable for plasma processing enter the substrate to be processed. Therefore, the anisotropy in the plasma processing can be increased.

For example, when etching a hole-like pattern, electrons and negative ions are supplied to the bottom of the hole by the incidence of negative ions. Therefore, when the high frequency component of the negative cycle is applied to the lower electrode after this timing, the positive ions can reach the bottom of the hole, and due to the presence of the sheath region, the positive ions can react with the electrons or the negative ions attached to the side wall of the hole. The effect of Coulomb force is suppressed. Therefore, high-speed etching into a more vertical shape becomes possible.

Further, for example, in the case of using for CVD, the anisotropy in the direction of the reaction gas can be increased, so that it is possible to satisfactorily fill the narrow gap of the underlying pattern.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic configuration diagram of a plasma processing apparatus according to a first embodiment of the present invention.

As shown in FIG. 1, an upper electrode 2 is provided on the inner wall of the upper end of the plasma processing vessel 1. Further, a lower electrode 3 is provided in the plasma processing vessel 1 so as to face the upper electrode 2, and a substrate 4 to be processed is placed on the lower electrode 3. A gas supply system 5 is provided on the upper surface of the upper electrode 2 and outside the plasma processing vessel 1. Further, a gas exhaust system 6 is provided below the plasma processing container 1, and the inside of the plasma processing container 1 is maintained at a constant pressure by exhausting a gas introduced from the gas supply system 5 and used for etching.

On the other hand, a first high-frequency power supply 7 and a second high-frequency power supply 8 for applying power between the electrodes 2 and 3
It is connected to the. The matching unit 9 combines high-frequency powers generated from the respective high-frequency power supplies 7 and 8 and performs impedance matching operation of plasma at the same time. The first high-frequency power supply 7 sends an output signal to the second high-frequency power supply 8 and modulates the high-frequency power of the second high-frequency power supply 8 to synchronize when the high-frequency power of the first high-frequency power supply 7 is in a negative cycle. .

FIG. 2 is a diagram showing output waveforms of the first high-frequency power supply 7 and the second high-frequency power supply 8 and output waveforms to which modulation has been applied. FIG. 2A shows an output waveform of the first high frequency power supply 7,
FIG. 2B shows an output waveform of the second high frequency power supply 8 and FIG.
(C) shows a waveform applied to the lower electrode 3, where the horizontal axis is time and the vertical axis is voltage. As shown in FIG.
The output waveform of the high-frequency power supply 7 is a waveform in which a positive cycle in which the input voltage is positive and a negative cycle in which the input voltage is negative are alternately repeated, and its frequency is 100 kHz. As shown in FIG. 2B, the output waveform of the second high-frequency power supply 8 has a frequency of 40.
A high frequency of 68 MHz appears. These first high frequency power supplies 7
When the power of the second high frequency power supply 8 and the power of the second high frequency power supply 8 are combined by the matching unit 9, an output waveform as shown in FIG. This output waveform is generated by modulating the negative cycle in the output waveform of the first high frequency power supply 7 so that the high frequency waveform of the second high frequency power supply 8 is synchronized.

The operation of the plasma processing according to the above embodiment will be described.

First, the substrate 4 to be processed is transported into the plasma processing vessel 1 by a transport mechanism (not shown), and is placed on the lower electrode 3. The processed substrate 4 has a silicon oxide film formed on the substrate, a resist is selectively formed on the silicon oxide film, and a fine hole pattern having a diameter of 0.15 μm is formed.

Then, the first high-frequency power source 7 shown in FIG.
The output waveform signal shown in (a) is output to the first high frequency power supply 7 and the matching device 9. In addition, the second high frequency power supply 8
The output waveform signal shown in FIG. The matching unit 9 combines high-frequency power from the first high-frequency power supply 7 and the second high-frequency power supply 8 to generate high-frequency power having an output waveform shown in FIG. Perform impedance matching operation. The power applied from the high frequency power supply 7 is 3000 W, and the power applied from the high frequency power supply 8 is 300 W.

When the high-frequency power is applied to the lower electrode 3, the gas supply system 5 supplies C ₄ F ₈ gas and Ar gas as etching gas at 20 sccm and 500 sc, respectively.
cm, and the plasma processing vessel 1 is maintained at 25 mTorr by a pressure gauge (not shown) to excite plasma.

Due to the excitation of the plasma, a plasma is generated between the upper electrode 2 and the lower electrode 3, and positive ions, negative ions, electrons, neutral active species and the like are generated. FIG. 2 (c)
Is applied to the lower electrode 3, the lower electrode 3 has a positive potential in a low frequency positive cycle, and not only electrons but also negative ions are efficiently supplied to the bottom of the hole. . When the electrons and negative ions are drawn into the substrate 4 to be processed, a sufficient amount of electrons and negative ions reach the bottom of the hole. On the other hand, the electrons are decelerated by the sheath region formed between the substrate 4 to be processed and the plasma, and adhere to the resist or the silicon oxide film.

Next, in the negative cycle, positive ions enter the substrate 4 to be processed. At the time of incidence on the substrate 4 to be processed, positive ions enter so as to be attracted to charges from electrons and negative ions that have reached the hole bottom.
Positive ions reach efficiently in the vertical direction. Accordingly, high-speed etching into a more vertical shape can be performed.

FIG. 3 is a diagram showing the relationship between the hole size and the etching depth in an experiment conducted under the conditions described in the present embodiment. In the experiments in the present embodiment, patterns having various hole dimensions were formed in a photoresist on a silicon oxide film having a thickness of 1 μm. For comparison, etching was similarly performed using a conventional plasma processing apparatus. The vertical axis represents the hole size, and the horizontal axis represents the etching depth.

As shown in FIG. 3, the hole size is 1.0 μm.
In the case of m, the etching depth is 1.0 μm in both the conventional example and the present embodiment, and it can be seen that the etching has progressed to the bottom surface of the silicon oxide film. When the hole size is reduced, in the case of the conventional example, the etching depth is sharply reduced, and the etching hardly progresses at the hole size of 0.15 μm, and it is impossible to etch more than about 0.1 μm. It was possible. This did not increase the etching depth even if the etching time was extended.

On the other hand, in the case of the present embodiment, the etching depth becomes somewhat shallower as the hole size becomes smaller. However, even when the hole size is set to 0.15 μm, the etching depth is 0.7 to 0.2 mm. About 8 μm is kept. From this, it can be seen that the etching is performed in the vertical shape.

In the positive cycle of the first high-frequency power supply 7, electrons having a proper amount of current and energy from the plasma are drawn into the bottom of the hole, and in the negative cycle, ions of fluorocarbon of a type suitable for etching are provided. It is considered that neutral particles reach the inside of the hole.

(Second Embodiment) FIG. 4 is a diagram showing an output waveform of a high-frequency power supply in a plasma process according to a second embodiment of the present invention. The plasma processing apparatus used in this embodiment is the same as that of the first embodiment shown in FIG.

FIG. 4 shows the output waveform of the high-frequency power applied to the lower electrode 3. After the first high-frequency power source 7 holds a potential of −50 V for a period of 500 microseconds,
A positive 150 V square wave is created with a positive cycle of 0 microseconds. In FIG. 4, the period of the negative potential and the period of the positive potential are indicated by A and B, respectively. The difference from the first embodiment is that the ratio between the periods A and B, that is, the duty ratio is changed.

While the first high frequency power supply 7 is in a negative period, the second high frequency power supply 8 outputs a high frequency of 40.68 MHz. At this time, the output of the second high frequency power supply 8 is 500 W.

The type, pressure, etc. of the gas introduced into the plasma processing vessel 1 are the same as those in the first embodiment.

As a result of etching under these conditions,
It has become possible to form a through hole of a silicon oxide film having a fine pattern of 0.15 μm by etching in a vertical shape. The period indicated by A was 500 microseconds, but the etching shape was not substantially changed even if it was changed from 200 microseconds to 10 milliseconds. In the period A, even when the potential was changed from -10 V to -500 V, the shape did not change.

On the other hand, when the period shown in B was changed from 50 microseconds to 500 microseconds, there was no significant difference in the etching shape. Also, the potential in the period shown in B was changed from 50 V to 200 V,
Similarly, there was no significant shape change. Here, the frequency of the second high frequency power supply 8 is 3 MHz or more and 110 MHz or less,
Desirably, the frequency is 10 MHz or more and 70 MHz or less.

FIG. 3 shows the relationship between the hole size and the etching depth in an experiment performed using the plasma processing method according to the present embodiment. As shown in FIG. 3, as in the first embodiment, as the hole size becomes smaller, the etching depth is sufficiently ensured as compared with the conventional example.

Further, as compared with the case of the first embodiment, it can be seen that the etching depth is further secured and the etching with high anisotropy is performed. this is,
By optimizing the duty ratio of the positive cycle and the negative cycle, the effect of electrons and negative ions reaching the hole bottom and the effect of attracting positive ions were balanced, and etching was performed efficiently. Conceivable.

As described above, according to the present embodiment, the anisotropy at the time of etching can be further increased by adjusting the duty ratio of the positive cycle and the negative cycle and applying the high-frequency power to the lower electrode 3. .

Note that the output of the high-frequency power supply shown in the first and second embodiments represents the effective power during continuous operation.

The present invention is not limited to the above embodiment.

The case where both the first high-frequency power supply and the second high-frequency power supply are connected to the lower electrode 3 has been described. However, whether one is connected to the upper electrode, the other is connected to the lower electrode, or both are connected to the upper electrode. The effect of the present invention is achieved. Also,
The number of power supplies is not limited to two, and three or more power supplies may be connected. Further, the present invention is not limited to the frequency, amplitude, and the like described in the above embodiment. In addition, although etching has been described as the plasma processing, the present invention is not limited to this, and can be applied to any plasma processing such as plasma CVD, plasma cleaning processing, and plasma downstream processing. The output waveform of the applied high-frequency power is not limited to a rectangular wave, but may be a triangular wave, a sine wave, or the like.

[0045]

As described above, according to the present invention, the output waveform of the low frequency component of the superimposed frequency power applied to the electrode has a positive cycle and a negative cycle, and the high frequency component is synchronized with the negative cycle. Thereby, the timing at which the positive cycle of the low frequency component is applied to the lower electrode on which the substrate to be processed is mounted is secured. Accordingly, electrons efficiently enter the substrate to be processed, and negative ions generated in the plasma simultaneously enter the substrate to be processed. Therefore, the anisotropy in the plasma processing can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a view showing an output waveform of the high-frequency power supply according to the embodiment.

FIG. 3 is a diagram showing a relationship between a hole size and an etching depth in an experiment performed using the plasma processing according to the embodiment.

FIG. 4 is a view showing an output waveform of a high-frequency power supply used for plasma processing according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of a conventional plasma processing apparatus.

FIG. 6 is a diagram for explaining a problem of the conventional plasma processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plasma processing container 2 ... Upper electrode 3 ... Lower electrode 4 ... Substrate to be processed 5 ... Gas introduction system 6 ... Gas exhaust system 7 ... 1st high frequency power supply 8 ... 2nd high frequency power supply 9 ... Matching circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05H 1/46 H05H 1/46 MF term (Reference) 4K030 DA04 FA03 JA18 KA49 4K057 DA12 DB20 DD03 DD08 DE06 DE14 DM01 DM02 DM08 DM16 DM17 DM18 DM20 DM31 DM33 DN01 5F004 BA04 BA09 BB11 BB18 BB28 CA09 DA00 DA23 DB03 EB01 5F045 AA08 AA19 DP01 DP02 DP03 EF05 EH13 EH14 EH19 EH20

Claims (4)

[Claims] 1. A substrate to be mounted on a lower electrode by plasma generated by applying high-frequency power to at least one of an upper electrode and a lower electrode disposed opposite to each other in a processing chamber. In the plasma processing method of performing a predetermined processing on the low frequency component, a low frequency component having a positive cycle and a negative cycle, and at least two types of frequencies having a high frequency component are superimposed to generate the high frequency power, A plasma processing method, wherein the high frequency component is applied to the electrode in synchronization with a negative cycle. 2. The low frequency component of the superimposed high frequency power is 2
The plasma processing method according to claim 1, wherein the frequency is 0 kHz or more and 400 kHz or less, and the high frequency component is 10 MHz or more and 70 MHz or less. 3. A pair of electrodes disposed opposite to each other in a processing chamber, a first power supply for supplying power having an output waveform of a low frequency component having a positive cycle and a negative cycle to the electrodes, A second power supply for supplying power having an output waveform to the electrode, wherein a high-frequency component of the second power supply is synchronized with a negative cycle of a low-frequency component of the first power supply to the electrode. A plasma processing apparatus for supplying electric power. 4. The low-frequency component of the superimposed high-frequency power is 2
4. The plasma processing apparatus according to claim 3, wherein the high-frequency component of the power is not less than 0 kHz and not more than 400 MHz and not more than 10 MHz and not more than 70 MHz.