JPH11224796A - Apparatus and method for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce abnormalities in the etching shape and generation of the micro-loading effect by further improving the uniformity of the charge distribution, and prevent degradation or breakage of a gate insulation film following the charge accumulation. SOLUTION: A spiral electrode 12 is provided on a chamber 10 through a dielectric plate 11, and the high-frequency pulse power for generating the plasma is supplied to the spiral electrode 12 from a high-frequency pulse power supply 13A. A sample base 14 is provided on a bottom part of the chamber 10, and a sample 15 to be etched is placed on the sample base 14. A DC pulse power supply 17 for bias is provided on a lower side of the sample base 14, and the sample base 14 is connected to the DC pulse power supply 17 through a strip line 16. The positive bias voltage is applied to the sample base 14 from the DC pulse power supply 17 during the period when no high-frequency power is supplied from the high-frequency pulse power supply 13A.

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 a plasma processing method using high-frequency discharge.

[0002]

2. Description of the Related Art Plasma processing methods using high-frequency discharge are used in various fields such as dry etching for fine processing, sputtering or plasma CVD for thin film formation, and ion implantation. In addition, plasma generation in a high vacuum is required for miniaturization of processing dimensions or high-precision control of film quality.

The following is an example of application of the plasma generation method.
Dry etching suitable for fine processing will be described.
Modern advances in high-density semiconductor integrated circuits are bringing about changes that can be compared to the industrial revolution, and higher densities in semiconductor integrated circuits are due to smaller element dimensions, improved devices, and larger chip sizes. It has been realized. The miniaturization of device dimensions has been progressing to the order of the wavelength of light, and the use of excimer lasers and X-rays for lithography is promising.
It can be said that dry etching plays an important role in realizing fine patterns along with lithography.

[0004] Dry etching is a process in which a sample to be etched is made unnecessary by utilizing a chemical or physical reaction between a gaseous phase such as radicals and ions existing in plasma and a solid phase surface to be etched. This is a processing technique for removing parts. Reactive ion etching (RIE), which is most widely used as a dry etching technique, causes an etching reaction by exposing a sample to be etched in a high-frequency discharge plasma composed of an appropriate reactive gas, thereby causing a surface of the sample to be etched to be etched. Unnecessary parts are removed. A necessary portion on the surface of the sample to be etched, that is, a portion that is not removed is protected by a resist pattern used as a photomask.

For miniaturization, it is necessary to make the directionality of ions uniform. For this purpose, it is essential to reduce the scattering of ions in plasma. It is effective to lower the pressure in the plasma generation chamber and increase the mean free path of the ions in order to make the directionality of the ions uniform. There is a new problem of lower rates.

As a countermeasure, a high-density plasma device such as an inductively coupled plasma device or a helicon type plasma device is being introduced. A high-density plasma device can generate plasma of one to two orders of magnitude higher than a conventional parallel plate RIE device. For this reason, even when the pressure in the plasma generation chamber is about one to two orders of magnitude lower, the RI
An etching rate equal to or higher than that of the E apparatus is obtained.

However, it has been found that the following problems occur in the high-density plasma apparatus as described above. That is, (1) abnormal etching shape due to charge-up, (2) microloading effect, and (3) deterioration or destruction of the gate insulating film. Hereinafter, a case where a gate electrode is formed by performing plasma etching on a conductive film (for example, a polycrystalline silicon film) deposited on a silicon substrate via an insulating film (for example, a silicon oxide film) using a resist pattern as a mask. The problem will be described.

(1) First, the occurrence of abnormalities in the etched shape due to charge-up will be described. A typical example of the occurrence of an abnormality in an etching shape due to charge-up is a notch phenomenon in etching of a conductive film. This notch phenomenon means that when a sample to be etched (conductive film) is etched by high-density plasma, the positive ions in the plasma have a large energy toward the sample to be etched, while the electrons in the plasma pass through the sample to be etched. The energy going is small. For this reason, in the isolated pattern region having a large space width, positive ions and electrons are accumulated in a well-balanced manner at the bottom of the sample to be etched (bottom of the space portion). A large amount of electrons are accumulated at the bottom of the sample to be etched (the bottom of the space), while a large amount of electrons are accumulated at the side of the sample to be etched (the side wall of the pattern portion). That is, a charge-up phenomenon occurs in which many electrons adhere to the side walls of the pattern portion. Therefore, the positive ions that approach the sample to be etched later are attracted to the side wall of the pattern portion, so that a wedge-shaped notch is formed at the bottom of the side wall of the pattern portion (for example, KKChi et al., DRY PROCESS SYMPOSIUM 1995). Proceedings, p.75, The Institute of Electrical Engineers of Japan. In particular, a notch is significantly formed at the bottom of the inner side wall of the outermost pattern in the dense pattern region.

(2) The localization and non-uniformity of the electric charge also affect the etching rate itself. That is, during etching, the resist mask is positively charged by the injected positive ions, so that in a region of the resist mask where the width of the mask opening is small, the function of preventing the positive ions from entering the mask opening works strongly. For this reason, the so-called microloading effect occurs in a region where the width of the mask opening in the resist mask is smaller, the lower the etching rate. Also, the microloading effect may appear as a difference in the etching angle of the pattern side wall between the isolated pattern region and the dense pattern region in the sample to be etched or a local difference in the base selectivity in the sample to be etched.

(3) Further, the imbalance of charge supply is M
There is a possibility that the gate insulating film of the OS transistor may be deteriorated or destroyed. For example, in plasma etching, a large amount of electric charge accumulated in a sample to be etched (conductive film) penetrates the gate insulating film and travels to the silicon substrate. At this time, a large electron current flows through the gate insulating film. The insulation of the film is deteriorated or destroyed. It is known that when the gate insulating film becomes extremely thin, about 10 nm or less, a phenomenon occurs in which the transconductance of the MOS transistor deteriorates, and in extreme cases, the dielectric breakdown of the gate insulating film is caused (for example, ERIGUCHI et al.,
IEICE TRANS. ELECTRON., VOL.E78-C, p.261, IEICE). In particular, the transistor size becomes 1 due to miniaturization.
When the thickness is equal to or less than μm, the LSI includes a transistor having a so-called antenna structure in which the area of the wiring is three to five digits or more of the area of the transistor. Since the antenna structure functions to increase the penetration of charges in the gate insulating film, it is considered that deterioration or destruction of the gate insulating film due to plasma becomes an increasingly important issue with miniaturization of transistors.

In order to solve the above-mentioned problem of the high-density plasma process, a pulse plasma process has been proposed (for example, Ohtake et al., DR in 1995).
YPROCESS SYMPOSIUM Proceedings, p.45, IEEJ).

Hereinafter, an etching apparatus for performing a pulse plasma process will be described with reference to FIG.

A spiral electrode 12 is provided via a dielectric plate 11 on a chamber 10 in which the inside is kept in a vacuum. One end of the spiral electrode 12 supplies a high-frequency pulse power for generating plasma. High frequency pulse power supply 13A
And the other end of the spiral electrode 12 is grounded. High-frequency pulse power is applied to the spiral electrode 12, and a high-density plasma is generated inside the chamber 10 by an induction electromagnetic field generated through the dielectric plate 11. A sample stage 14 is provided at the bottom of the chamber 10, and a sample 15 to be etched is placed on the sample stage 14. The sample stage 14 and the high frequency power supply source 20 for bias are connected via a strip line 16. Plasma data of the plasma generation region 18 is obtained by a microwave interferometer 19 provided on the side wall of the chamber 10.

[0014]

However, in the above-described pulsed plasma process in which high-frequency power for plasma generation is supplied in a pulsed form, the above-described abnormalities in the etching shape due to charge-up and the microloading effect are reduced. Although it can be reduced to some extent, there is a problem that the effect of reducing these is not sufficient.

Further, the above-mentioned pulsed plasma process comprises:
Deterioration or destruction of the gate insulating film due to accumulation of electric charges by high-density plasma etching also has a problem that it will not be sufficiently effective in reducing the thickness of the gate insulating film in the future.

In view of the above, it is an object of the present invention to reliably prevent a charge-up phenomenon from occurring in a film to be processed formed on a substrate to be processed. It is an object of the present invention to further improve the uniformity of the charge distribution, further reduce the occurrence of abnormalities in the etching shape and the occurrence of the microloading effect, and to prevent the gate insulating film from being deteriorated or destroyed due to the accumulation of charges.

[0017]

In order to achieve the above object, the present invention is to apply a positive bias voltage to a sample to be etched when a high frequency pulse power for generating plasma is off.

[0018] A plasma processing apparatus according to the present invention includes a vacuum chamber provided with a sample stage for holding a substrate to be processed and having gas introduction means for introducing a reactive gas;
A reactive gas supply means for supplying a reactive gas to the vacuum chamber, and a predetermined level of high-frequency power intermittently or repeatedly supplied to the vacuum chamber or a high-level and low-level high-frequency power alternately and repeatedly supplied to the vacuum chamber. A high-frequency power supply unit for generating a plasma made of a reactive gas in the chamber, and a period in which high-frequency power of a predetermined level is not supplied from the high-frequency power supply unit or a period in which low-level high-frequency power is supplied from the high-frequency power supply unit And a bias voltage supply means for applying a positive bias voltage to the sample stage.

According to the plasma processing apparatus of the present invention, the positive bias is applied during the period when the high-frequency power supply unit does not supply the predetermined high-frequency power or when the low-frequency power supply unit supplies the low-level high-frequency power. A bias voltage supply means for applying a voltage to the sample stage, so that a positive bias voltage can be applied to the sample stage when the high-frequency power for plasma generation is off or at a low level; Electrons attached to the target film on the substrate can be drawn into the target substrate, and negative ions in the plasma can be drawn into the target film on the target substrate.

In the plasma processing apparatus of the present invention, the impedance between the sample stage and the bias voltage supply means is preferably set to 1.0Ω or less.

In the plasma processing apparatus of the present invention, it is preferable that the sample stage and the bias voltage supply are connected via a strip line.

In the plasma processing apparatus of the present invention, it is preferable that the bias voltage supply means is provided on the sample table on the side opposite to the substrate to be processed held on the sample table.

In the plasma processing apparatus of the present invention, a high impedance with respect to a predetermined level of high frequency power or a high level of high frequency power supplied from the high frequency power supply means is provided between the sample stage and the bias voltage supply means. It is preferable that a band rejection filter be provided.

In the plasma processing apparatus of the present invention, one end is grounded between the sample stage and the bias voltage supply means, and a predetermined level of high-frequency power or high-level high-frequency power supplied from the high-frequency power supply means is provided. It is preferable that the other end of the bandpass filter having low impedance with respect to the frequency is connected.

In the plasma processing apparatus of the present invention, it is preferable that the bias voltage supply means comprises a pulse signal source and a high-band amplifier connected in series.

In this case, the high-band amplifier preferably has a frequency band that is at least twice the repetition frequency of the pulse signal output from the pulse signal source.

In the plasma processing apparatus according to the present invention, the bias voltage supply means is preferably a DC pulse power supply.

In this case, the bias voltage supply means is more preferably a bipolar DC pulse power supply.

In the plasma processing method according to the present invention, a reactive gas is supplied to a vacuum chamber in which a sample stage holding a substrate to be processed is provided, and a high-frequency power is repeatedly and intermittently supplied to the vacuum chamber. A step of generating a plasma made of a reactive gas in the vacuum chamber, and a step of applying a positive bias voltage to the sample stage during at least a part of the period in which no high-frequency power is supplied.

According to the plasma processing method of the present invention, during the period when the high-frequency power for plasma generation is not supplied, or during the period when the low-frequency high-frequency power is supplied from the high-frequency power supply means, the sample table is positively charged. Since the bias voltage is applied, electrons attached to the processing target film on the processing target substrate are drawn into the processing target substrate, and negative ions in the plasma are drawn into the processing target film on the processing target substrate. The charge-up phenomenon can be reduced and the phenomenon that the film to be processed is positively charged can be eliminated.

In the plasma processing method of the present invention, it is preferable that a predetermined delay time is set between the time when the supply of the high frequency power is stopped and the time when the application of the positive bias voltage is started. .

The plasma processing method of the present invention preferably further comprises a step of applying a negative bias voltage to the sample stage during at least a part of the period during which the high-frequency power is supplied.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A dry etching apparatus and a dry etching method according to a first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic view showing the structure of a dry etching apparatus according to the first embodiment of the present invention.
, 10 is grounded, the inner wall is ceramic,
The chamber is covered with an insulating material such as Teflon or quartz and the inside thereof is kept in a vacuum. Note that the chamber 10 may have a double structure having an inner chamber made of quartz or the like instead of a structure in which the inner wall is covered with an insulator. Further, the chamber 10 includes the chamber 10
A well-known gas introducing means for introducing a reactive gas is provided therein, but is not shown.

As shown in FIG. 1, a spiral electrode 12 is provided on a chamber 10 via a dielectric plate 11 made of ceramic or the like, and one end of the spiral electrode 12 is connected to a high-frequency pulse power supply 13A. The other end of the spiral electrode 12 is grounded. As a result, high-frequency pulsed power is applied to the spiral electrode 12, and an induced electromagnetic field generated via the dielectric plate 11 causes
0 to generate high density plasma. At the bottom of the chamber 10, a metal sample stage 14 whose surface is coated with an insulating material is provided. On the sample stage 14, a sample 15 to be etched as a substrate to be processed is provided. It is placed.

As a feature of the first embodiment, as shown in FIG. 1, a bias DC
A pulse power supply 17 is provided, and the sample stage 14 and the DC pulse power supply 17 having a bias amount are connected by a strip line 16 having a length of about 30 cm. When the sample 15 to be etched is held on the lower surface of the sample stage 14, it is preferable to provide a DC pulse power source 17 for bias near the upper portion of the sample stage 14.

The strip line 16 is in the form of a strip made of copper having a width of 2 cm and a thickness of 0.5 mm, and is covered with a metal square tube at an interval of 2 to 3 cm. Is suppressed. Since the sample stage 14 and the DC pulse power supply 17 are connected via the strip line 16, an increase in parasitic capacitance or an increase in inductance between the sample stage 14 and the DC pulse power source 17 can be suppressed.

By reducing the impedance of the strip line 16, the waveform of the bias DC pulse output from the DC pulse power supply 17 can be faithfully adjusted.
It is important to tell. In other words, unless the impedance of the strip line 16 is sufficiently lower than the impedance between the sample stage 14 and the plasma generation region 18, the bias voltage is applied to the sheath region between the sample stage 14 and the plasma generation region 18. This is because the ions are not applied and the ions cannot be accelerated. Assuming that the area of the sample stage 14 is 300 cm ² and the thickness of the sheath region is 1 mm, the capacitance of the sheath region is about 300 pF.
In order to achieve the RC time constant for transmitting high-frequency power having a frequency of 200 MHz, the impedance of the sheath region needs to be set to approximately 17Ω or less. Considering the influence of the contact resistance and the parasitic inductance at the connection part of the strip line 16, the impedance needs to have a margin of one digit or more. Therefore, the impedance between the sample stage 14 and the DC pulse power supply 17 for bias is 1
Must be set to Ω or less.

As shown in FIG. 1, a microwave interferometer 19 is attached to a window provided on the side wall of the chamber 10, and the microwave interferometer 19 acquires plasma data for a desired time.

Hereinafter, a dry etching method according to the first embodiment, which is performed using the dry etching apparatus according to the first embodiment, will be described with reference to FIG. FIG. 2 shows changes over time of various parameters in the dry etching method according to the first embodiment.

High frequency pulse power supply 13A for plasma generation
After a predetermined delay time Td since the high-frequency pulse power applied from the power supply is turned off, the bias DC pulse power supply 17 is turned on, and the DC pulse power supply 17
To apply a positive bias voltage.

Since a reactive gas used for etching, for example, a halogen gas is an electron-negative gas, in a state after the high-frequency pulse power for plasma generation is turned off, that is, in an after-glow plasma state, the acceleration of electrons is accelerated. Since there is no source, the electron temperature drops and electron attachment and dissociation tend to occur, so that the electron density drops rapidly. On the other hand, contrary to the decrease in electron density, negative ions increase rapidly due to the occurrence of electron attachment and dissociation. Usually, the delay time Td is preferably set to a time at which the electron density decreases to a predetermined ratio or less with respect to the peak value, for example, half or less of the peak value, preferably to about 1/10 of the peak value.

When the delay time Td is set so that the bias DC pulse power supply 17 is turned on after the electron density in the plasma becomes equal to or less than the set ratio with respect to the peak value, the delay time Td elapses, that is, the DC pulse power supply 17 When a positive bias voltage is applied to the sample stage 14, when the electron density is sufficiently low and the negative ion density is large,
The electron current flowing into the sample 4 can be made sufficiently small to effectively extract a negative ion current, and the sample 15 can be effectively irradiated with negative ions.

As a reactive gas, 50 sccm of HBr gas and 25 sccm of Cl ₂ gas were introduced into the chamber 10, and the pressure in the chamber 10 was adjusted to 1 to 3 Pa. Thereafter, a high-frequency pulse power supply 13A for plasma generation
Therefore, the frequency is 13.56 MHz and the pulse width is 10
A high-frequency pulse power having a time average power of 500 to 1000 W for 30 μsec was applied to the spiral electrode 12. Further, a positive bias voltage of 30 to 150 V was applied from a DC pulse power supply 17 for biasing with a pulse width of 0.1 to 10 μsec. The pulse repetition frequency of the positive bias voltage is 10
kHz, and the delay time Td was set to 30 to 70 μsec.

After elapse of about 20 μs after turning off the high frequency pulse power supply 13 for plasma generation, the electron density was reduced to less than half, and a rapid decrease in the electron density in the afterglow plasma was observed.

When the phosphorus-doped polycrystalline silicon film deposited on the silicon oxide film was etched using the plasma generated by the etching method of the first embodiment, the etching rate was 300 to
The etching rate was 800 nm / sec, the selectivity to the silicon oxide film was 20 to 100, the etching characteristics were good, and the etching shape was anisotropic. No notch phenomenon and abnormal pattern shape due to charge-up were not observed.

As described above, according to the first embodiment, when the high-frequency pulse power supplied from the plasma-generating high-frequency pulse power supply 13A is off, the bias DC pulse power supply 17 supplies the sample stage 14 with the high-frequency pulse power. Since a positive bias voltage is applied to the sample 15 to be etched, the following effects can be obtained.

Electrons adhering to the side of the sample 15 to be etched (side walls of the pattern) are drawn into the substrate, and negative ions in the plasma are drawn to the bottom of the sample 15 to be etched (bottom of the space region). In addition, the charge-up phenomenon is reduced, and a situation in which a wedge-shaped notch is formed at the bottom of the side wall of the pattern can be avoided.

Since the negative ions in the plasma are drawn into the resist mask formed on the sample 15 to be etched, the positive charges on the resist mask are eliminated by the negative ions, thereby avoiding the microloading effect.

Since the negative ions in the plasma are attracted to the sample 15 to be etched, the negative ion current flows and the electron current that flows instantaneously increases, so that the peak value of the current flowing in the insulating film decreases. A situation in which the insulating property of the gate insulating film is deteriorated or broken can be avoided.

Since the negative ions in the plasma are drawn into the sample 15 to be etched, the etching is performed even when the high frequency pulse power supplied from the high frequency pulse power supply 13A for plasma generation is off, so that the etching rate is improved. . In the conventional etching method using no high-frequency pulse power, a phenomenon was observed in which the etching rate of the dense pattern was faster than that of the isolated pattern. However, according to the first embodiment, the etching of the isolated pattern and the dense pattern was performed. There was little difference between the rates.

In particular, when the electron density is greatly reduced from the peak value, the DC pulse power supply 17 for biasing is used.
When the delay time Td is set so as to turn on, a positive bias voltage is applied to the sample 15 to be etched when the negative ions are greatly increased because the electron density is greatly reduced. Negative ions in the plasma can be effectively drawn into the sample to be etched.

According to the first embodiment, it is considered that the reason why the charge-up phenomenon is surely reduced is that the negative ions in the plasma are drawn into the sample 15 to be etched. That is, when high-energy positive ions or negative ions are incident on the sample to be etched, the charge of the incident ions is accumulated on the surface of the sample to be etched. The effect of the secondary electrons emitted from is also so large that it cannot be ignored. When positive ions are incident, the emission of secondary electrons acts to increase the accumulation of positive charges, but when negative ions are incident, the emission of secondary electrons acts to cancel the accumulation of negative charges. .

(Second Embodiment) Hereinafter, a dry etching apparatus and a dry etching method according to a second embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a schematic diagram showing the structure of a dry etching apparatus according to a second embodiment of the present invention. In the second embodiment, the same members as those in the first embodiment shown in FIG.

The difference between the dry etching apparatus according to the second embodiment and the first embodiment is that the high-frequency pulse power supply 13B for plasma generation alternately outputs high-level high-frequency power and low-level high-frequency power alternately. And a bipolar DC pulse power supply 21 for alternately and repeatedly applying a negative bias voltage and a positive bias voltage to the sample table 14 in place of the DC pulse power supply 17 for bias.

Hereinafter, a dry etching method according to the second embodiment, which is performed using the dry etching apparatus according to the second embodiment, will be described with reference to FIG. FIG. 4 shows changes over time of various parameters in the dry etching method according to the second embodiment.

As shown in FIG. 4, when the high-frequency pulse power supply 13B for plasma generation outputs high-level high-frequency power, the bipolar DC pulse power supply 21 for bias is used.
Applies a negative bias voltage to the sample stage 14, and after a predetermined delay time Td after the high-frequency pulse power supply 13B outputs low-level high-frequency power, the bipolar DC pulse power supply 2
1 applies a positive bias voltage to the sample stage 14.

In the second embodiment, when the high-frequency pulse power supply 13B outputs high-level high-frequency power,
Since the bipolar DC pulse power supply 21 applies a negative bias voltage to the sample stage 14, positive ions are attracted to the surface of the sample 15 to be etched.

Similarly to the first embodiment, after a predetermined delay time Td from the output of the high-frequency pulse power supply 13B of the low-frequency high-frequency power, the bipolar DC pulse power supply 2
When 1 applies a positive bias voltage to the sample stage 14, electrons and negative ions are drawn. The high-frequency pulse power supply 13B outputs a low-level high-frequency power, but there is no significant difference from the first embodiment in the decrease in electron density and the increase in negative ion density.

According to the second embodiment, the bipolar DC
When the pulse power supply 21 applies a negative bias voltage to the sample table 14, positive ions are irradiated on the sample 15 to be etched, and the bipolar DC pulse power supply 21
When a positive bias voltage is applied to the sample 15, the sample 15 is irradiated with negative ions, so that the etching rate can be improved and etching with excellent anisotropy can be performed.

As a reactive gas, 50 sccm of HBr gas and 25 sccm of Cl ₂ gas were introduced into the chamber 10, and the pressure in the chamber 10 was set to 1 to 3 Pa. Then, the high frequency pulse power supply 13B for plasma generation
Therefore, the frequency is 13.56 MHz and the pulse width is 10
30 μs, 500 when time average power is high level output
~ 1000W, 50 ~ 200W for low level output
Is applied to the spiral electrode 12. Further, a negative bias voltage of −50 to −200 V is applied from the bias bipolar DC pulse power supply 21 in synchronization with the high-level high-frequency power from the high-frequency pulse power supply 13B, and the low-level pulse is supplied from the high-frequency pulse power supply 13B. After a predetermined delay time Td from the application of the high-frequency power, a positive bias voltage of 30 to 150 V is set to 10 to 30 μm.
It was applied with a pulse width of seconds. The pulse repetition frequency is 1
0 kHz and the delay time Td was set to 30 to 70 μsec.

When the phosphorus-doped polycrystalline silicon film deposited on the silicon oxide film was etched using the plasma generated by the etching method of the second embodiment, the etching rate was 350 to 350.
The etching rate was 800 nm / sec, the selectivity to the silicon oxide film was 20 to 100, the etching characteristics were good, and the etching shape was anisotropic. No notch phenomenon and abnormal pattern shape due to charge-up were not observed.

(Third Embodiment) Hereinafter, a dry etching apparatus and a dry etching method according to a third embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a schematic diagram showing the structure of a dry etching apparatus according to the third embodiment of the present invention. In the third embodiment, the same members as those in the first embodiment shown in FIG.

The dry etching apparatus according to the third embodiment is different from the first embodiment in that a negative bias voltage and a positive bias voltage are alternately applied to the sample stage instead of the bias DC pulse power supply 17. Bipolar DC applied to 14
A pulse power supply 21 is provided, and a band rejection filter 22 having a high impedance with respect to the frequency of the high frequency pulse power for plasma generation is inserted in the strip line 16.

According to the third embodiment, since the band rejection filter 22 having a high impedance with respect to the frequency of the high frequency pulse power for plasma generation is inserted in the middle of the strip line 16, the high frequency pulse for plasma generation is inserted. Power is supplied from the sample stage 14 to the bipolar DC pulse power source 2
1 prevents the bipolar DC pulse power supply 21 from being destroyed or the bias voltage from being applied to the sample stage 14 becoming unstable.

As a reactive gas, 50 sccm of HBr gas and 30 sccm of Cl ₂ gas were introduced into the chamber 10, and the pressure in the chamber 10 was adjusted to 1 to 5 Pa. Thereafter, a high-frequency pulse power supply 13A for plasma generation
The frequency is 54 MHz and the pulse width is 10-50 μ
A high-frequency pulse power having a time average power of 300 to 700 W for 2 seconds was applied to the spiral electrode 12. After a predetermined delay time Td from when the high frequency pulse power supplied from the high frequency pulse power supply 13A stops from the bias bipolar DC pulse power supply 21, a positive bias voltage of 50 to 100 V is applied for 10 to 30 seconds. The pulse width was applied. The repetition frequency of the positive bias voltage was set to 5 to 10 kHz, and the delay time Td was set to 70 μs.

When the phosphorus-doped polycrystalline silicon film deposited on the silicon oxide film was etched using the plasma generated by the etching method of the third embodiment, the etching rate was 200 to
The etching rate was 300 nm / sec, the selectivity to the silicon oxide film was 50 or more, the etching characteristics were good, and the etching shape was anisotropic. No notch phenomenon and abnormal pattern shape due to charge-up were not observed.

(Fourth Embodiment) Hereinafter, a dry etching apparatus and a dry etching method according to a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a schematic diagram showing the structure of a dry etching apparatus according to the fourth embodiment of the present invention. In the fourth embodiment, the same members as those in the first embodiment shown in FIG.

The difference between the dry etching apparatus according to the fourth embodiment and the first embodiment is that the high-frequency pulse power supply 13B for generating plasma alternately outputs high-level high-frequency power and low-level high-frequency power. A bipolar DC pulse power supply 21 for alternately applying a negative bias voltage and a positive bias voltage to the sample stage 14 in place of the DC pulse power source 17 for bias; And the band pass filter 23 is inserted between them.

In the dry etching method according to the fourth embodiment, similarly to the second embodiment, when the high frequency pulse power supply 13B for plasma generation outputs a high level of high frequency power, the bipolar DC pulse power supply for bias is used. 21 applies a negative bias voltage to the sample stage 14, and after a predetermined delay time Td from when the high-frequency pulse power supply 13B outputs low-level high-frequency power, the bipolar DC pulse power source 21 applies a positive bias voltage to the sample stage. 14, the period in which the high-frequency pulse power supply 13B outputs high-level high-frequency power does not completely coincide with the period in which the bipolar DC pulse power supply 21 applies a negative bias voltage to the sample stage 14. That is, the period during which the bipolar DC pulse power supply 21 applies a negative bias voltage to the sample stage 14 may be slightly shorter or slightly longer than the period during which the high-frequency pulse power supply 13B outputs high-level high-frequency power. Or may be slightly delayed. Even in this case, since the positive ions are attracted to the surface of the sample 15 to be etched with high energy, it is effective when it is necessary to perform etching at high energy, such as when etching a silicon oxide film. It is.

C ₄ F ₈ gas of 50 sccm was introduced into the chamber 10 as a reactive gas, and the pressure in the chamber 10 was adjusted to 3 to 10 Pa. Thereafter, a frequency of 13.56 MHz is supplied from the high frequency pulse power supply 13B for plasma generation.
z, the pulse width is 10 to 50 μsec, and the time average power is 50
A high-frequency pulse power of 0 to 1500 W is supplied to the spiral electrode 12.
Was applied. Further, a bipolar DC pulse power supply 21 for bias supplies a negative bias voltage of -500 V and 1
A positive bias voltage of 00V was applied with a pulse width of 10-50 sec. The pulse repetition frequency is 5 kHz,
The delay time Td was set to 100 μs.

When the BPSG (boron / phosphorus glass) film was etched using the plasma generated by the etching method of the fourth embodiment, the etching rate was 500 to 800 nm / sec. The selectivity to the substrate was 50 or more, the etching characteristics were good, and the etching shape was anisotropic.

(Fifth Embodiment) Hereinafter, a dry etching apparatus and a dry etching method according to a fifth embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a schematic view showing a structure of a dry etching apparatus according to a fifth embodiment of the present invention. In the fifth embodiment, the same members as those in the first embodiment shown in FIG.

The dry etching apparatus according to the fifth embodiment is different from the fourth embodiment in that a signal generator 24 for outputting a high-frequency pulse signal instead of the bipolar DC pulse power supply 21 and a DC to 200 MHz A broadband amplifier 25 for amplifying a broadband high-frequency pulse signal is provided.

In this manner, the signal generator 24 and the broadband amplifier 25 not only supply a positive or negative bias voltage having a square wave but also a positive or negative bias voltage having a desired waveform such as a sawtooth wave. It can be applied to the platform 6. Generally, a single DC pulse power supply has a maximum output of about several hundred watts. However, if a DC pulse power supply including the signal generator 24 and the broadband amplifier 25 is provided, a bias voltage larger than several hundred watts is applied. be able to.

It is preferable that wide band amplifier 25 has a frequency band at least twice the repetition frequency of the signal output from signal generator 24. By doing so, the wide area amplifier 25 can accurately amplify the pulse signal output from the signal generator 24.

The fifth embodiment is the same as the fourth embodiment except that the configuration of the DC pulse power supply is different. Therefore, the same etching characteristics as those of the fourth embodiment can be obtained.

In the first to fifth embodiments, the case of the etching apparatus using high-density plasma has been described. However, instead of this, the high-density plasma is used, such as a plasma CVD apparatus or a sputtering apparatus. Even if it is applied to a required device, charge-up can be effectively prevented.

[0083]

According to the plasma processing apparatus of the present invention, a positive bias voltage can be applied to the sample stage when the high frequency power for plasma generation is off or at a low level. Electrons attached to the processing film can be drawn into the processing target substrate, and negative ions in the plasma can be drawn into the processing target film on the processing target substrate, so that the charge-up phenomenon can be reduced. At the same time, the phenomenon that the film to be processed is positively charged can be eliminated.

Therefore, when the plasma processing apparatus of the present invention is used in an etching apparatus, the following effects can be obtained.

Electrons adhering to the side of the sample to be etched (sidewalls of the pattern portion) are drawn into the substrate to be processed and negative ions in the plasma are drawn to the bottom of the sample to be etched (bottom of the space). Therefore, the charge-up phenomenon is reduced, and a situation in which a wedge-shaped notch is formed at the bottom of the side wall of the pattern can be avoided.

Since negative ions in the plasma are drawn into the resist mask formed on the sample to be etched, the positive charge on the resist mask is eliminated.
The micro loading effect can be avoided.

Since the negative ions in the plasma are attracted to the sample to be etched, the negative ion current flows and the electron current that flows instantaneously increases, and the peak value of the current flowing in the insulating film decreases. It is possible to avoid a situation in which the insulation property is deteriorated or destroyed.

Since the negative ions in the plasma are attracted to the sample to be etched, the etching is performed even when the high frequency pulse power for plasma generation is off, so that the etching rate is improved.

In the plasma processing apparatus of the present invention, if the impedance between the sample stage and the bias voltage supply means is set to 1.0Ω or less, the waveform of the bias voltage applied to the sample stage from the bias voltage supply means Can be prevented from becoming dull.

In the plasma processing apparatus according to the present invention, when the sample stage and the bias voltage supply unit are connected via a strip line, an increase in parasitic capacitance or an increase in inductance between the sample stage and the bias voltage supply unit is prevented. Can be suppressed.

In the plasma processing apparatus of the present invention, if the bias voltage supply means is provided on the side opposite to the substrate to be processed held on the sample table, the distance between the sample table and the bias voltage supply means can be shortened. In addition, an increase in impedance between the sample stage and the bias voltage supply unit can be suppressed.

In the plasma processing apparatus of the present invention, a band rejection filter having a high impedance with respect to the frequency of the high frequency power supplied from the high frequency power supply is provided between the sample stage and the bias voltage supply. When,
A situation in which the high-frequency power supplied from the high-frequency power supply means reaches the bias voltage supply means through the sample table, and the bias voltage supply means is destroyed or the bias voltage applied to the sample table becomes unstable. Can be avoided.

In the plasma processing apparatus of the present invention, a ground-connected band-pass filter having a low impedance with respect to the frequency of the high-frequency power supplied from the high-frequency power supply is provided between the sample stage and the bias voltage supply. The high-frequency power supplied from the high-frequency power supply means reaches the bias voltage supply means through the sample stage, and the bias voltage supply means is destroyed or the bias voltage applied to the sample stage becomes unstable. Can be avoided.

In the plasma processing apparatus of the present invention, when the bias voltage supply means comprises a pulse signal source and a high-band amplifier connected in series, a bias voltage having a desired waveform can be applied to the sample table and a bias with a large power can be applied. A voltage can be applied to the sample stage.

In this case, if the high-band amplifier has a frequency band that is at least twice the repetition frequency of the pulse signal output from the pulse signal source, the bias voltage applied to the sample stage from the bias voltage supply means Can be prevented from becoming dull.

In the plasma processing apparatus of the present invention, when the bias voltage supply means is a DC pulse power supply, a positive bias voltage can be easily and reliably applied to the sample stage.

In this case, if the bias voltage supply means is a bipolar DC pulse power supply, a positive bias voltage and a negative bias voltage can be applied to the sample stage.

According to the plasma processing method of the present invention, a positive bias voltage can be applied to the sample stage when the high-frequency power for plasma generation is off, so that the film adheres to the film to be processed on the substrate to be processed. Electrons can be drawn into the substrate to be processed and negative ions in the plasma can be drawn into the film to be processed on the substrate to be processed, so that the charge-up phenomenon can be reduced and the film to be processed can be reduced. The phenomenon of positive charging can be eliminated.

In the plasma processing method of the present invention, if a predetermined delay time is set between the time when the supply of the high frequency power is stopped and the time when the application of the positive bias voltage is started, the electron density is reduced. When the negative ions greatly increase due to a large decrease with respect to the peak value, a positive bias voltage is applied to the film to be processed on the substrate to be processed. Can be effectively drawn into the film to be processed.

When the plasma processing method of the present invention includes a negative bias applying step of applying a negative bias voltage to the sample stage when high-frequency power is supplied, positive ions in the plasma are converted into the substrate to be processed. It can be drawn into the target film above. Therefore, when the plasma processing method of the present invention is applied to an etching method, the etching rate is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a dry etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a time change of various parameters in the dry etching method according to the first embodiment of the present invention.

FIG. 3 is a sectional view illustrating a schematic configuration of a dry etching apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a time change of various parameters in a dry etching method according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a schematic configuration of a dry etching apparatus according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a schematic configuration of a dry etching apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view showing a schematic configuration of a dry etching apparatus according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing a schematic configuration of a conventional dry etching apparatus.

[Explanation of symbols]

 Reference Signs List 10 chamber 11 dielectric plate 12 spiral electrode 13A, 13B high frequency pulse power supply 14 sample table 15 sample to be etched 16 strip line 17 DC bias power supply 18 plasma generation area 19 μ wave interferometer 21 bipolar DC pulse power supply 22 band stop filter 23 band Pass filter 24 Signal generator 25 Broadband amplifier

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/302 B

Claims (13)

[Claims] A vacuum chamber provided with a sample stage for holding a substrate to be processed and having a gas introducing means for introducing a reactive gas; and a predetermined level of high-frequency power intermittently and repeatedly supplied to the vacuum chamber. High frequency power supply means for generating a plasma comprising the reactive gas in the vacuum chamber by alternately or repeatedly supplying a high level and a low level high frequency power, and the predetermined level from the high frequency power supply means. Bias voltage supply means for applying a positive bias voltage to the sample stage during a period in which high-frequency power is not supplied or a period in which the low-level high-frequency power is supplied from the high-frequency power supply means. A plasma processing apparatus characterized by the above-mentioned. 2. The plasma processing apparatus according to claim 1, wherein the impedance between the sample stage and the bias voltage supply unit is set to 1.0Ω or less. 3. The plasma processing apparatus according to claim 1, wherein the sample stage and the bias voltage supply unit are connected via a strip line. 4. The plasma processing apparatus according to claim 1, wherein said bias voltage supply means is provided on a side of said sample stage opposite to a substrate to be processed held on said sample stage. apparatus. 5. A high impedance between the sample stage and the bias voltage supply means with respect to the frequency of the predetermined level of high frequency power or the high level of high frequency power supplied from the high frequency power supply means. The plasma processing apparatus according to claim 1, further comprising a band rejection filter. 6. A high-frequency power of the predetermined level or the high-level high-frequency power supplied from the high-frequency power supply means, one end of which is grounded between the sample stage and the bias voltage supply means. 2. The plasma processing apparatus according to claim 1, wherein the other end of the band-pass filter having a low impedance with respect to the other end is connected. 7. The plasma processing apparatus according to claim 1, wherein said bias voltage supply means comprises a pulse signal source and a high-band amplifier connected in series. 8. The plasma processing apparatus according to claim 7, wherein the high-band amplifier has a frequency band that is at least twice the repetition frequency of the pulse signal output from the pulse signal source. 9. The plasma processing apparatus according to claim 1, wherein said bias voltage supply means is a DC pulse power supply. 10. The plasma processing apparatus according to claim 9, wherein said bias voltage supply means is a bipolar DC pulse power supply. 11. A reactive gas is supplied to a vacuum chamber in which a sample stage holding a substrate to be processed is provided, and high-frequency power is intermittently supplied to the vacuum chamber so that the vacuum chamber is supplied to the vacuum chamber. Generating a plasma of the reactive gas; and applying a positive bias voltage to the sample stage during at least a part of the period when the high-frequency power is not supplied. Plasma processing method. 12. A predetermined delay time is set between a time when the supply of the high-frequency power is stopped and a time when the application of the positive bias voltage is started. 4. The plasma processing method according to 1. 13. The plasma processing method further comprising a step of applying a negative bias voltage to the sample stage during at least a part of a period during which the high-frequency power is supplied.