JPH09326383A - Plasma processing system and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the generation quantity and the quality of ions or radicals required for surface reaction and to enhance the selectivity and the like of plasma processing by obtaining a narrow ion energy distribution with high controllability. SOLUTION: The plasma processing system comprises a vacuum processing chamber 10, a stage 15 for arranging a sample to be processed in the vacuum processing chamber, and a plasma generation means including a high frequency power supply 16. The plasma processing system further comprises a pair of parallel plate electrodes 12, 15, means 20, 22, 23 for holding a sample 40 to the sample stage through electrostatic attraction, and means 17 for applying a bias voltage to the sample. Metastable atoms generated in a plasma generation chamber for generating metastable atoms are injected into the vacuum processing chamber 10 and applied with the high frequency power supply 16 of 10-500MHz while reducing the pressure in the vacuum processing chamber 10 to 5-50mTorr by means of a vacuum pump 18.

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, and more particularly to a plasma processing apparatus and a plasma processing method suitable for forming a fine pattern in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 6-267900 discloses a high frequency stop time of 10 microseconds and a repetition frequency of 10
It is described that a high frequency power source that is ON-OFF pulse modulated at a frequency of kHz or higher is used to control the dissociation reaction and the ion temperature to improve the accuracy of etching. In this publication, N
The pulse stop time and plasma density characteristics for _two gas plasmas are described, and considering that the interval time, which is the pulse stop time, does not decrease the pulse density.
It is stated that 0 microseconds or less is optimal. On the other hand, when the pulse width is reduced with CHF3 plasma and the pulse stop time is fixed at 10 microseconds, the ratio of undesired F radicals to preferred CF2 radicals: F
/ CF2 is reduced, and the selectivity with respect to the underlying silicon is improved in the oxide film etching. However, in this example, it is shown that if the pulse stop time is 10 microseconds or more, the plasma density is lowered and the etching rate is also lowered, which is not preferable.

Further, in the technical field of performing etching processing and film forming processing of semiconductors using plasma, plasma is applied to a sample table on which an object to be processed (for example, a semiconductor wafer substrate, hereinafter referred to as a sample) is placed. US Pat. No. 5,320,982 discloses a processing apparatus provided with a high frequency bias power source for accelerating ions in the sample and an electrostatic adsorption film for holding a sample on a sample table by electrostatic adsorption force. There is something.

The apparatus described in US Pat. No. 5,320,982 generates plasma by microwaves and holds a sample on a sample table by electrostatic attraction force, and at the same time, a heat transfer gas is provided between the sample and the sample table. While controlling the temperature of the sample through the interposition, a high frequency power source for sine wave output is used as a bias power source, and the power source is connected to the sample stage to control the ion energy incident on the sample.

Further, in Japanese Laid-Open Patent Publication No. 62-280378, a pulsed ion control bias waveform for stabilizing the electric field strength between the plasma electrode and the electrode is generated and applied to the sample stage so that the ion energy incident on the sample is It is described that the distribution width can be narrowed and the processing dimensional accuracy of etching and the etching rate ratio between the film to be processed and the base material can be increased several times.

Further, in Japanese Patent Laid-Open No. 6-61182,
It is described that plasma is generated by using electron cyclotron resonance, and a pulse bias having a pulse duty of about 0.1% or more is applied to a sample to prevent the generation of a notch.

[0007]

FIG. 1 shows an electron energy distribution (hereinafter abbreviated as EEDF) when a direct current discharge is generated with argon gas at a relatively high gas pressure (1 Torr).
Is shown by a solid line and the Maxwell distribution is shown by a dotted line. In order to ionize a normal gas, electron energy of about 15 electron volts (hereinafter abbreviated as eV) or more is required. On the other hand, in most cases, electron energy of about 10 eV or less is sufficient for dissociating the gas used for plasma processing of semiconductors. Therefore, considering only gas dissociation, electrons with high energy of 15 eV or more are not necessary, and dissociation proceeds too much and dissociates into too fine radicals, molecules or atoms, which is more harmful. As shown by the solid line in FIG. 1 above, in a region where the gas pressure is high, collisions between electrons and gas frequently occur,
The number of high-energy electrons of about 15 eV or more is small. Therefore, the above adverse effects can be suppressed to a relatively low level. However, the processing pressure is 50 mT in order to cope with the recent finer patterning in the semiconductor manufacturing process.
It has become necessary to make it less than orr. In this low pressure region, the EEDF approaches the Maxwell distribution shown by the dotted line in FIG. 1, the number of high-energy electrons of about 15 eV or more increases, ionization becomes active, the number of ions increases, and the plasma density also increases. The above-mentioned adverse effects have become remarkable especially in the oxide film etching process. This tendency becomes more remarkable when high power is injected and a sample is processed with high-density plasma in order to speed up the process.

That is, at present, a plasma satisfying all three requirements of low pressure, high density, and prevention of excessive dissociation has not been obtained.

Japanese Unexamined Patent Publication No. 267900 mentioned in the above-mentioned conventional example.
In the publication, excessive dissociation is prevented by applying a high-frequency electric field that is turned on and off at a stop time of 10 microseconds or less and a repetition frequency of 10 kHz or more, but it is still insufficient. In this method, in order to sufficiently prevent excessive dissociation, it is necessary to set the stop time to 10 microseconds or more, but with the increase in the stop time, the processing speed is greatly reduced, and there is a great disadvantage that it becomes impractical. .

Further, the pulse bias power supply method described in JP-A-62-280378 and JP-A-6-61182 uses a dielectric layer for electrostatic attraction between the sample stage electrode and the sample. The application of pulse bias to the sample has not been studied.If it is applied to the electrostatic adsorption method as it is, the ion energy distribution is widened due to the change in the voltage generated across the electrostatic adsorption film. However, there is a drawback in that it is impossible to deal with the necessary processing of a fine pattern while performing control.

Further, in the conventional sine wave output bias power supply system described in USP 5,320,982,
When the frequency becomes higher, the impedance of the sheath approaches the impedance of the plasma itself or becomes lower than that, so unnecessary plasma is generated by the bias power source and it is not used effectively for accelerating ions, and the plasma distribution deteriorates and There are drawbacks such as changes in the type of particles generated and loss of controllability of ion energy by the bias power source.

The object of the present invention is to solve the problems of the prior art as described above, and to control the production amount and quality of ions and radicals and to improve the temperature controllability by electrostatic adsorption of the sample. Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method for performing required processing of a fine pattern with high accuracy and stability.

Another object of the present invention is to control the quantity and quality of ions and radicals produced, obtain a narrow ion energy distribution, and stabilize the plasma at a high speed with good controllability to improve the selectivity of plasma processing. And a plasma processing method.

Another object of the present invention is to control the amount and quality of ion and radical generation and to process a sample under a relatively low gas pressure, thereby facilitating precise processing of fine patterns and performing plasma processing. It is an object of the present invention to provide a plasma processing apparatus and a plasma processing method in which the selection ratio, the speed, etc. are improved.

Another object of the present invention is to control the amount and quality of ions and radicals produced and to control the insulating film (eg SiO2,
It is an object of the present invention to provide a plasma processing apparatus and a plasma processing method in which the selectivity and speed of plasma processing with respect to SiN, BPSG, etc.) are improved.

[0016]

Means for Solving the Problems One of the present invention is to effectively utilize the property that plasma generation characteristics greatly change depending on the type and number of metastable atoms that are present in plasma in relatively small amounts. It controls the quantity and quality of each of them fairly independently. That is, in order to generate a metastable atom, 8 to 2
It requires a fairly high energy of 0 eV, but ionization easily occurs at a low energy of about 5 eV or less in the presence of metastable atoms. By setting different places or timings of generating metastable atoms and places or timings of generating relatively low energy plasma in the presence of a large number of metastable atoms and setting them separately, the amount of ions and radicals can be controlled. The quality controllability can be greatly improved.

That is, a large number of metastable atoms are generated by the first plasma generating means for generating a strong plasma with a high-frequency source having a large instantaneous power, and the instantaneous power is generated while the metastable atoms are present in the vacuum processing chamber. The first plasma generating means for generating a relatively weak plasma with a high-frequency source having a small number generates a radical that is not excessively dissociated from the ions.

With this configuration, 50 mTo
Even in a high-density plasma at a low gas pressure of about rr or less, an EEDF similar to that shown by the solid line in FIG. 1 or having a lower electron temperature and significantly less high-energy electrons of 15 eV or more can be obtained. .

That is, it becomes possible to prevent low gas pressure-high density-excessive dissociation, which cannot be achieved by conventional plasma. Here, the number of ions is mainly determined by the number of metastable atoms by the first plasma generation means, while the number and quality of radicals are mainly determined by the second plasma generation means. The place where the first plasma is generated is different from the place where the second plasma is generated, or the place where the second plasma is generated is the same place but the timing of generating the plasma is different. The invention can be applied.

In order to obtain high-performance processing performance by using the ions and radicals generated as described above, the energy of the ions incident on the sample must be a predetermined magnitude and energy.
It is necessary to narrow the distribution width of. For this purpose, it is preferable to apply a pulsed bias voltage to the sample stage. In addition, in order to improve the temperature controllability of the sample, the sample is electrostatically adsorbed on the sample table and the thickness of several microns to several tens of microns is used for several Torr.
It is configured to conduct heat through a gas layer of several tens of torr.

A feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generating means,
An electrostatic adsorption means for holding the sample on the sample table by an electrostatic adsorption force, a bias application means for applying a bias voltage to the sample, and a first plasma for generating plasma inside or outside the vacuum processing chamber. The production means and the second plasma production means for producing plasma in the vacuum processing chamber are provided to control the quantity and quality of the production of ions and radicals.

A feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generating means,
An electrostatic adsorption means for holding the sample on the sample table by an electrostatic adsorption force, a bias application means for applying a bias voltage to the sample, and a first plasma for generating plasma inside or outside the vacuum processing chamber. It is provided with a generation means and a second plasma generation means for generating plasma in the vacuum processing chamber, and the instantaneous power of the first plasma generation means is at least twice the instantaneous power of the second plasma generation means. In addition, it is set to 100 times or less to control the quantity and quality of ion and radical generation.

Another feature of the present invention is to provide a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a first plasma generating chamber inside or outside the vacuum processing chamber. Plasma generation means, second plasma generation means for generating plasma in the vacuum processing chamber, electrostatic attraction means for holding the sample on the sample stage by electrostatic attraction force, and application of a pulse bias voltage to the sample Pulse bias applying means for controlling the quantity and quality of ion and radical generation.

Another feature of the present invention is that a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a first plasma generating chamber inside or outside the vacuum processing chamber. Plasma generation means, second plasma generation means for generating plasma in the vacuum processing chamber, electrostatic attraction means for holding the sample on the sample stage by electrostatic attraction force, and application of a pulse bias voltage to the sample And a pulse bias applying means for controlling the quantity and quality of ion and radical generation to 10 MHz as the plasma generation source.
A high-frequency voltage of up to 500 MHz is applied and the vacuum processing chamber is decompressed to 5 mTorr to 50 mTorr.

Another feature of the present invention is that a vacuum processing chamber, a sample stand for placing a sample to be processed in the vacuum processing chamber,
A first plasma generating means for generating plasma inside or outside the vacuum processing chamber, a second plasma generating means for generating plasma in the vacuum processing chamber, and the sample on the sample stage by electrostatic attraction. An electrostatic attraction means for holding the sample and a pulse bias applying means for applying a pulse bias voltage to the sample, and a voltage generated corresponding to the electrostatic attraction capacity of the electrostatic attracting means with the application of the pulse bias voltage. Is provided to control the amount and quality of ion and radical production.

Another feature of the present invention is that a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber,
A first plasma generating means for generating plasma inside or outside the vacuum processing chamber, a second plasma generating means for generating plasma in the vacuum processing chamber, and the sample on the sample stage by electrostatic attraction. The electrostatic attraction means for holding, the pair of opposing electrodes on which the sample is arranged on one electrode, and the one electrode at the time of etching the sample, 250
A pulse bias applying means for applying a pulse bias voltage having a pulse amplitude of V to 800 V and a duty ratio of 0.05 to 0.4 is provided, and the amount and quality of ions and radicals are independently controlled, and Insulating film (eg SiO2,
SiN, BPSG, etc.) with the plasma.

Another feature of the present invention is to place a sample on a sample stage installed in a vacuum processing chamber, to hold the placed sample on the electrode by electrostatic attraction, and to introduce a gas. And a step of first plasma-converting the introduced gas into plasma, and a second plasma-processing to further plasma-convert into an atmosphere in which the sample is placed containing at least the plasma-converted gas. And the step of etching the sample with the plasma and the step of applying a bias voltage to the electrode of the sample stage at the time of the etching, which controls the amount and quality of the generation of ions and radicals to increase the selectivity of the reaction. In addition to the above, the plasma processing method has both anisotropy of processing and high-speed processing.

Another feature of the present invention is that the instantaneous value of the power supplied in the first plasma conversion step is at least twice the instantaneous value of the power supplied in the second plasma conversion step, and 1
This is a plasma processing method in which the amount and quality of ion and radical generation are controlled to increase the selectivity of the reaction by setting the ratio to 00 times or less, and at the same time, the anisotropy of the processing and the speeding up of the processing are combined.

Another feature of the present invention is that a sample is placed on one of a pair of opposing electrodes provided in a vacuum processing chamber, the sample is held on the electrode by electrostatic attraction, and a gas is used. A step of introducing a gas, and a step of forming a plasma into a plasma of the introduced gas;
A second plasma-izing step of applying a high-frequency voltage of 10 MHz to 500 MHz to further plasma in an atmosphere in which the sample containing at least the plasma-converted gas is placed; and etching the sample with the plasma. Step, applying a bias voltage to the electrode of the sample stage during the etching, and setting the atmosphere to 5 mT
This is a plasma processing method which comprises a step of evacuating under reduced pressure to orr to 50 mTorr to control the amount and quality of ion and radical generation to achieve high selectivity of the reaction, and at the same time, anisotropy of the processing and speeding up of the processing. .

Another feature of the present invention is to dispose a sample on one of the electrodes facing each other, to hold the arranged sample on the electrode by electrostatic attraction, and to introduce gas. A step of first plasma-converting the introduced gas into plasma, and a second plasma-processing of further plasma-converting into an atmosphere in which the sample is placed containing at least the plasma-converted gas. A step of etching the sample with the plasma, and a step of applying a bias voltage to the electrode of the sample stage during the etching, and a pulse amplitude of 250 V to 800 V and 0 to the sample stage electrode during the etching. The step of applying a pulse bias voltage having a duty ratio of 0.05 to 0.4, and Controls, there insulating film (e.g. SiO2, SiN, BPSG, etc.) in the sample to be plasma treated.

Another feature of the present invention is that, in the above plasma processing apparatus, the first plasma generating means and the second plasma generating means are each a high-output timing portion of one pulse-modulated high-frequency power source. This is a plasma processing apparatus that controls the amount and quality of ions and radicals generated to improve the accuracy of the reaction in correspondence with the low-output timing portion, and also has the anisotropy of the processing and the speeding up of the processing.

According to the present invention, the amount and quality of ions and radicals produced are controlled to improve the accuracy of the reaction, and a predetermined amount is provided on the sample table equipped with electrostatic adsorption means having a dielectric layer for electrostatic adsorption. By applying the pulsed bias power supply having the characteristic, the temperature controllability of the sample can be sufficiently performed, and the necessary fine pattern processing can be stably performed at high speed with good anisotropy.

Further, it is possible to control the quantity and quality of the generation of ions and radicals, obtain a narrow ion energy distribution, and improve the selectivity of the plasma treatment stably and with good controllability.

Further, according to the present invention, the quantity and quality of ion and radical generation are controlled, and the change in the voltage generated corresponding to the electrostatic adsorption capacity of the electrostatic adsorption means due to the application of the pulse bias voltage is suppressed. As a voltage suppressing means for changing the voltage applied to both ends of the dielectric layer by electrostatic attraction during one pulse cycle,
The pulse bias voltage is configured to be 1/2 or less. Specifically, the thickness of the dielectric electrostatic chuck film provided on the surface of the lower electrode is reduced, or the dielectric is made of a material having a large relative dielectric constant. Alternatively, a method may be adopted in which the cycle of the pulse bias voltage is shortened to suppress a rise in the voltage applied to both ends of the dielectric layer.

Further, according to the present invention, the amount and quality of ion and radical generation are controlled, and a pulse amplitude of 250 V to 800 V and 0.05 V is applied to the one electrode during etching of the sample.
By applying a pulse bias voltage having a duty ratio of ~ 0.4, the insulating film (eg SiO2,
It is possible to improve the selectivity of plasma treatment for SiN, BPSG, etc.).

Further, according to another feature of the present invention, the amount and quality of ions and radicals produced are controlled, a high frequency voltage of 10 MHz to 500 MHz is used as a high frequency power source for plasma generation, and the gas pressure in the processing chamber is controlled. The low pressure is 5 mTorr to 50 mTorr. Thereby, a stable plasma can be obtained. Further, by using such a high frequency voltage, the ionization of the gas plasma is improved, the control of the selection ratio during sample processing is improved, and high-speed processing can be obtained with a relatively low ion energy, so that the sample is damaged. Ji can be held low.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. First, FIG. 2 shows a first embodiment in which the present invention is applied to a facing electrode type plasma etching apparatus.

In FIG. 2, a processing chamber 1 as a vacuum container.
0 is provided with a pair of opposing electrodes consisting of an upper electrode 12 and a lower electrode 15. The gap between the parallel plate electrodes 12 and 15 is preferably about 10 mm to 50 mm. A high frequency power supply 1 for supplying high frequency energy to the upper electrode 12.
6 are connected via a high frequency power source modulation signal source 161. An upper electrode cover 30 is provided on the lower surface of the upper electrode 12 as a fluorine or oxygen removing plate made of silicon, carbon, or SiC. Further, a gas introduction chamber 34 having a gas diffusion plate 32 that diffuses the gas into a desired distribution is provided above the upper electrode 12. In the processing chamber 10, gas necessary for processing such as etching of a sample is supplied from the gas supply unit 36 through the gas diffusion plate 32 of the gas introduction chamber 34, the holes 38 provided in the upper electrode 12 and the upper electrode cover 30. Supplied. The outer chamber 11 has a valve 1 in the outer chamber.
A vacuum pump 18 connected via 4 evacuates the processing chamber 10 to the processing pressure of the sample. A discharge containment ring 37 is provided around the processing chamber 10.

The parallel plate electrodes 12 in the present invention,
It suffices that 15 has a pair of electrodes facing each other, and the parallel plate electrodes 12 and 15 may have a concave surface or a convex surface in view of requirements such as plasma generation characteristics.

The lower electrode 15 for holding the sample 40 has a two-pole type electrostatic chuck 20. That is, the lower electrode 15 includes the outer first lower electrode 15A,
A dielectric layer for electrostatic adsorption (hereinafter, abbreviated as electrostatic adsorption film) is formed on the upper surface of the first and second lower electrodes by the second lower electrode 15B disposed above the inside thereof with the insulator 21 interposed therebetween. 22) is provided. A DC power supply 23 is connected between the first and second lower electrodes via high frequency component cutting coils 24A and 24B, and the second lower electrode 15 is connected.
A DC voltage is applied between both lower electrodes so that the B side becomes positive. This allows the sample 40 to pass through the electrostatic adsorption film 22.
And Coulomb force acting between both lower electrodes
Are adsorbed and held on the lower electrode 15. Electrostatic adsorption film 22
For example, a dielectric material such as aluminum oxide or a mixture of aluminum oxide and titanium oxide can be used. Also, as the power supply 23, several hundreds of volts
Use the DC power source.

A pulse bias power supply 17 for supplying a positive pulse bias of 20V to 800V is connected to the lower electrodes 15 (15A, 15B) via blocking capacitors 19A, 19B for cutting DC components. There is.

When the etching process is performed, the sample 40, which is the object of the process, is placed on the lower electrode 15 of the processing chamber 10 and adsorbed by the electrostatic chuck 20. On the other hand, a gas necessary for etching the sample 40 is supplied from the gas supply unit 36 to the processing chamber 10 via the gas introduction chamber 34. The outer chamber 11 is evacuated by a vacuum pump 18, and the processing chamber 10 is processed at a sample processing pressure, for example, 5 mTorr to 50 mTorr.
Is exhausted under reduced pressure. Next, from the high frequency power source 16, 10 MHz to 500 MHz, preferably 30 MHz to 200 MHz.
The high frequency power of MHz is output to turn the processing gas in the processing chamber 10 into plasma. On the other hand, the lower electrode 15 has a voltage of 20 V to 800 V and a period of 0.1 μm from the pulse bias power supply 17.
s to 10 μs, preferably 0.2 μs to 5 μs, and a positive pulse bias with a pulse width of 0.05 μs to 0.5 μs is applied to control the energy of electrons and ions incident on the sample to obtain a predetermined value for the sample 40. The etching process is performed.

The high frequency power source 16 is pulse modulated by the high frequency power source modulation signal source 161 with a pulse width of 1 to 50 μs, a pulse period of 20 μs to 1 ms, and a pulse duty ratio (pulse width / pulse period) of 1/3 to 1/50. Therefore, the instantaneous power of the pulse width portion is applied with a strength that is 2 to 100 times stronger than the instantaneous power of the other timing portion, and metastable atoms are efficiently generated in the pulse width portion. On the other hand, in the other timing portions, a high frequency plasma having a relatively low instantaneous power is applied in the presence of the metastable atoms to promote ionization to obtain high density plasma, and at the same time, 15 eV
The above-mentioned generation of high-energy electrons is suppressed to prevent excessive dissociation of the processing gas, and promote dissociation with electron energy of about 10 eV or less, which is relatively low, which is desirable for plasma processing. Although electrons with high energy are generated in the pulse width portion where the instantaneous power is large, electrons with high energy disappear in a few μs, so the pulse duty ratio is set to 1
The effect is reduced by setting the value to a low value of ⅓ or less, preferably ⅕ or less and setting the pulse period to 20 μs or more. Further, the metastable atom has a long life and continues to exist for a period of several tens μs to several hundreds μs even when the disappearance due to collision is taken into consideration. In the other timing portions described above, the existence of the metastable atoms efficiently causes ionization even with relatively low energy electrons of about 5 eV or less, so that a high density plasma is maintained without the presence of high energy electrons. It The number of radicals causing surface reaction and the degree of dissociation are controlled by changing the instantaneous power of the other timing portions. On the other hand, the number of ions is mainly controlled by changing the instantaneous power of the pulse width portion. Preferably, the instantaneous power of the pulse width portion is 2 to 100 times, preferably 5 to 20 times as strong as the instantaneous power of the other timing portions, and metastable atoms are added in the pulse width portion. In addition to efficient generation, it prevents excessive dissociation in other timing parts and secures the necessary number of radicals.

The etching gas is distributed by the gas diffusion plate 32 to a desired distribution, and then the upper electrode 12 and the upper electrode cover 3 are formed.
It is injected into the processing chamber 10 through a hole 38 drilled.

The upper electrode cover 30 is made of carbon, silicon, or a material containing these, and fluorine or oxygen components are removed to improve the selectivity with respect to the base such as resist or silicon.

Insulating film (eg, SiO2, BPSG, etc.)
As an example of the gas species in the case of performing the etching treatment on rare earth, rare gas: 200 ccm, C4F8: 10 ccm, gas pressure: 2
At 0 mTorr, when utilizing metastable atoms of rare gas (helium, neon, argon, xenon, etc.) to promote ionization of the rare gas itself; rare gas 1: 200 ccm, rare gas 2:
20ccm, C4F8: 10ccm, gas pressure 20mTorr
In order to promote the ionization of rare gas 2 (argon, krypton, xenon, etc.) having an ionization level lower than its energy level by utilizing metastable atoms of rare gas 1 (helium, neon, etc.) There is. In this way, high energy
By reducing the number of electrons in C4F8, excessive dissociation of C4F8 can be prevented, and a large amount of CF2, which is convenient for insulating film treatment, can be generated. By changing the ratio of the rare gas to the C4F8 gas, the ratio of the amounts of ions and radicals can be changed. To further improve characteristics such as selectivity, a gas containing a hydrogen component (CHF3, CH2F2, CH3F, CH4, CH3OH, etc.) may be added.

The discharge containment ring 37 localizes the plasma around the sample chamber 40 to improve the plasma density and the outside of the discharge containment ring 37. Minimize unnecessary deposition of deposits on the

It should be noted that as the discharge stopping ring 37, it is preferable to use an insulator such as quartz. However, using a semiconductor or conductive material such as carbon, silicon, or SiC,
By connecting to a high frequency power source and causing sputtering by ions, it is possible to reduce deposition of deposits on the ring 37 and also to have an effect of removing fluorine and oxygen.

On the insulator 13 around the sample 40,
When the susceptor cover 39 containing carbon or silicon or these is provided, fluorine and oxygen can be removed, which is useful for improving the selection ratio.

Further, the lower electrode 15 (15A, 15A) is sandwiched by the electric potential of the DC power supply 23 with the electrostatic attraction film 22 of the dielectric material interposed therebetween.
An electrostatic adsorption circuit is formed via B) and the sample 40. In this state, the sample 40 is moved to the lower electrode 15 by electrostatic force.
It is locked and retained by. Sample 4 locked by electrostatic force
A cooling gas such as helium, nitrogen, or argon is supplied to the back surface of 0. The cooling gas fills the concave portion of the lower electrode 15, and the pressure thereof is in the range of several torr to several tens of torr. Note that the electrostatic attraction force is almost zero between the concave portions where the gap is provided, and it can be considered that the electrostatic attraction force is generated only at the convex portion of the lower electrode 15.
However, as will be described later, since the voltage can be appropriately set in the DC power supply 23 and the adsorption force that can sufficiently withstand the pressure of the cooling gas can be set, the sample 40 is moved or skipped by the cooling gas. There is nothing to do.

In order to improve the fine workability of the sample, it is preferable to use a higher frequency power source 16 for plasma generation and to stabilize the discharge in the low gas pressure region. In the present invention, the processing pressure of the sample in the processing chamber 10 is 5 mTorr to 50 mTorr. By reducing the gas pressure in the processing chamber 10 to a low pressure of 50 mTorr or less, the collision of ions in the sheath is reduced, so that the directionality of ions is increased during the processing of the sample 40, and vertical fine processing is enabled. . At 5 mTorr or less, in order to obtain the same processing speed, the size of the exhaust device and the high-frequency power source are increased, and more than necessary dissociation occurs due to an increase in the electron temperature, which tends to deteriorate the characteristics.

Generally, between the frequency of the power source for plasma generation using the parallel plate electrodes and the lowest gas pressure for stable discharge, the higher the frequency of the power source and the greater the distance between the electrodes, There is a relationship that the minimum gas pressure for stable discharge decreases. Surrounding wall and discharge confinement ring 37
In order to avoid the adverse effect of deposits on the upper electrode cover 30, the susceptor cover 39, and the resist and the like in the sample to effectively remove the fluorine and oxygen, the average free process of 30 at the maximum gas pressure of 50 mTorr is used. It is desirable to set the distance between the electrodes to about 50 mm or less in correspondence with the double or less.
If the distance between the electrodes is not more than about 2 to 4 times (3 mm to 6 mm) of the mean free path at the maximum gas pressure (50 mTorr), stable discharge becomes difficult.

In the embodiment of the present invention shown in FIG. 2, the high frequency power source 16 for plasma generation is 10 MHz to 500 MHz.
Since a high frequency power of z, preferably 30 MHz to 200 MHz is used, the gas pressure in the processing chamber is 5 mTorr to 50 mTorr.
Even if the pressure is low, stable plasma can be obtained, and fine workability can be improved. Further, by using such high-frequency power, the dissociation of gas plasma is improved, and the selectivity control during sample processing is improved.

By the way, the electrostatic adsorption film 22 acts so as to inhibit the action of the pulse bias on the ions. In the present invention, the electrostatic adsorption film 22 is applied with the application of the pulse bias.
One of the features is that the voltage suppressing means is provided in order to suppress the rise of the voltage generated between both ends and to enhance the effect of the pulse bias.

As an example of the voltage suppressing means, a change in voltage (V _CM ) during one cycle of the bias voltage generated between both ends of the electrostatic adsorption film due to the application of the pulse bias is the magnitude of the pulse bias voltage (V _CM ). _It is preferable to configure it to be 1/2 or less of _p ). Specifically, the electrostatic capacitance of the dielectric is reduced by reducing the thickness of the electrostatic attraction film made of the dielectric provided on the surface of the lower electrode 15 or by using a material having a large dielectric constant. There is a way to increase.

Alternatively, as another voltage suppressing means,
There is also a method of suppressing the rise of the voltage V _CM by shortening the cycle of the pulse bias voltage. Furthermore, a method in which the electrostatic suction circuit and the pulse bias voltage application circuit are separately provided at different positions, for example, at an opposite electrode different from the electrode on which the sample is arranged and held, or at a third electrode separately provided is also considered. Can be

Next, the relationship between the pulse bias voltage and the change in voltage (V _CM ) generated across the electrostatic adsorption film during one cycle of the pulse bias, which should be brought about by the voltage suppressing means in the present invention, will be described with reference to FIGS. This will be described in detail with reference to FIG.

First, an example of a desirable output waveform used in the pulse bias power supply 17 of the present invention is shown in FIG. In the figure, the pulse amplitude is v _p , the pulse period is T ₀ , and the positive direction pulse width is T ₁ .

When the waveform of FIG. 3 (A) is applied to the sample via the blocking capacitor and the dielectric layer for electrostatic adsorption (hereinafter abbreviated as electrostatic adsorption film), plasma is generated by another power source. The potential waveform on the surface of the sample in the steady state in this state is shown in FIG.

However, the direct current component voltage of the waveform: V _DC The floating potential of the plasma: V _f The maximum voltage in one cycle of the voltage generated across the electrostatic adsorption film is V _CM .

In FIG. 3 (B), the portion (I) where the positive voltage is higher than V _f is the portion that mainly draws only the electron current, and the negative portion from V _f is the ionic current. The part where _Vf is drawn is a part where electrons and ions are balanced ( _Vf is usually several V to ten and several V).

Incidentally, in FIG. 3 (A) and the following description,
It is assumed that the capacity of the blocking capacitor and the capacity of the insulator near the surface of the sample are sufficiently larger than the capacity of the electrostatic attraction film (hereinafter simply referred to as electrostatic attraction capacity).

The value of V _CM is expressed by the following equation (Equation 1).

[0064]

[Equation 1]

However, q: ion current density (average value) flowing into the sample during the period (T ₀ −T ₁ ) c: electrostatic adsorption capacity per unit area (average value) i _i : ion current density, ε _r : Relative permittivity of electrostatic adsorption film d: film thickness of electrostatic adsorption film ε ₀ : dielectric constant (constant) in vacuum K: electrode coverage of electrostatic adsorption film (≦ 1) The pulse duty ratio: (T ₁ / T ₀ ) shows a probability distribution of the potential waveform and ion energy of the sample surface when T ₀ is changed while keeping it constant. Where T ₀₁ ,
T ₀₂ : T ₀₃ : T ₀₄ : T ₀₅ = 16: 8: 4: 2: 1.

As shown in FIG. 4A, the pulse period T ₀
Is too large, the potential waveform on the sample surface deviates greatly from the rectangular wave and becomes a triangular wave, and the ion energy has a constant distribution from the lower side to the higher side, which is not preferable.

As shown in (2) to (5) of FIG. 4, as the pulse period T ₀ is decreased, (V _CM / v _p ) becomes a value smaller than 1, and the ion energy distribution also narrows. .

4 and 5, T ₀ = T ₀₁ , TO ₀₂ ,
T ₀₃ , T ₀₄ , and T ₀₅ are (V _CM / v _p ) = 1, 0.63,
It corresponds to 0.31, 0.16, and 0.08.

Next, the pulse off (T ₀ -T ₁ ) period, and
FIG. 6 shows the relationship between the maximum voltage V _{CM in} one cycle of the voltage generated across the electrostatic adsorption film.

As the electrostatic adsorption film, a titanium oxide-containing alumina having a thickness of 0.3 mm (ε _r = 10) was used.
% (K = 0.5), the ion current density i _i
The change in the value of V _CM in the medium density plasma of = 5 mA / cm ² is shown by the thick line (standard condition line) in FIG.

As is clear from FIG. 6, as the pulse off (T ₀ -T ₁ ) period becomes longer, the voltage V _CM generated across the electrostatic adsorption film becomes a larger value in proportion to it, which is normally used. The applied pulse voltage becomes _vp or more.

[0072] For example, in a plasma etching apparatus, damage, selectivity with the base or the mask, typically the shape or the like, in the gate etch 250Volt ≦ a 50volt ≦ v _p ≦ 200volt oxide film etched by 20volt ≦ v _p ≦ 100volt metal etching Limited to v _p ≤ 800 volt.

When the condition of (V _CM / v _p ) ≦ 0.5 described later is to be satisfied, the upper limit of (T ₀ −T ₁ ) is as follows in the standard state.

For gate etching, (T ₀ −T ₁ ) ≦
0.15μs metal in the etching (T ₀ -T ₁₎ ≦ 0.35μs oxide film in the etching (T ₀ -T ₁₎ ≦ 1.2μs Incidentally, when T ₀ is close to 0.1 .mu.s, the impedance of the ion sheath plasma Since the impedance becomes close to or lower than the impedance of, the plasma is generated undesirably and the bias power supply is not effectively used for accelerating ions. Therefore, since the control of the ion energy by the bias power source is degraded, T ₀ is, 0.1 [mu]
s or more, preferably 0.2 μs or more.

Therefore, in a gate etcher or the like in which v _p can be kept low, the dielectric constant of the material of the electrostatic adsorption film is 1
0 to 100 (eg, ε _r = 2 in Ta ₂ O ₃₎
5) or a thin film thickness without lowering the withstand voltage, for example, 10 μm to 400 μm, preferably 10 μm to 10 μm.
It needs to be 0 μm.

In FIG. 6, the electrostatic capacity c per unit area is
V _CM when increased by 2.5 times, 5 times and 10 times respectively
The value of is also shown. Even if the electrostatic adsorption film is improved, at present it is considered that the improvement of the capacitance c by several times is the limit, and V _CM ≦ 3
Assuming that 00 volt and c ≦ 10c ₀ , 0.1 μs ≦ (T ₀ −
T ₁ ) ≦ 10 μs.

The portion effective for plasma treatment by the acceleration of ions is the portion (T ₀ -T ₁ ), and the pulse duty (T ₁ / T ₀ ) is preferably as small as possible.

FIG. 7 shows the efficiency of the plasma treatment estimated by (V _DC / v _p ) in consideration of the time average. (T
_It is preferable to decrease ₁ / T ₀ ) and increase (V _DC / v _p ).

The plasma processing efficiency is 0.5 ≦ (V _DC
/ V _p ) and the following condition, (V _CM / v _p ) ≦ 0.5
, The pulse duty is (T ₁ / T ₀ ) ≦ 0.
It will be about 4.

The smaller the pulse duty (T ₁ / T ₀ ) is, the more effective it is to control the ion energy. However, if it is made smaller than necessary, the pulse width T ₁ becomes a small value of about 0.05 μs, which is several tens of MHz. Therefore, it becomes difficult to separate it from the high frequency component for plasma generation, which will be described later. As shown in FIG. 7, 0 ≦ (T ₁ /
When (T ₀ ) ≦ 0.05, the decrease of (V _DC / v _p ) is slight, and when (T ₁ / T ₀ ) is 0.05 or more, no particular problem occurs.

Here, as an example of gate etching, FIG. 8 shows etching rates ESi and ESiO between silicon and an underlying chloride film when chlorine gas of 10 mT is turned into plasma.
₂ shows the ion energy dependence of ₂ . The silicon etching rate ESi has a constant value at low ion energy. When the ion energy is about 10 V or more, ESi increases as the ion energy increases. On the other hand, the etching rate ESiO ₂ of the underlying oxide film is 0 when the ion energy is about 20 V or less, and when it exceeds about 20 V, ESiO ₂ increases with the ion energy.

As a result, when the ion energy is about 20 V or less, there is a region where the selection ratio ESi / ESio ₂ with respect to the base becomes ∞. When the ion energy is about 20 V or more, the selectivity ESi / ESiO ₂ with respect to the base rapidly decreases as the ion energy increases.

FIG. 9 shows an oxide film (Si
As an example of etching (O ₂ , BPSG, HISO, etc.), an etching rate ESiO ₂ and ES of an oxide film and silicon when C 4 F 8 gas 10 mT is turned into plasma
It shows the ion energy distribution of i.

The etching rate ESiO ₂ of the oxide film is
At low ion energies, the value is negative and a depot occurs.
When the ion energy is around 400 V, ESiO ₂ rises rapidly and positively, and thereafter gradually increases. On the other hand, the etching rate ESi of the underlying silicon is ESi
At a place where the ion energy is higher than O ₂ , (−) (etching) is changed to (+) (etching), and gradually increases.

As a result, in the vicinity of the change of ESiO ₂ from (-) to (+), the selection ratio ESiO ₂ / ESi with the base is
、, above which ESiO ₂ / ESi drops rapidly with increasing ion energy.

In FIG. 8 and FIG. 9, the values of ESi and ESiO ₂ and ESi / ESi are applied to the actual process.
The ion energy is adjusted to an appropriate value by adjusting the bias power source in consideration of the magnitudes of O ₂ and ESiO ₂ / ESi.

Further, until just etching (etching until the underlying film appears), the size of the etching rate is prioritized, and after the just etching, the ion energy is changed before and after the just etching by prioritizing the size of the selection ratio. If so, better characteristics can be obtained. In the case of etching a multilayer film, the characteristics can be improved by changing the ion energy value even before just etching and setting the optimum value at each timing.

The characteristics shown in FIGS. 8 and 9 are characteristics when the ion energy distribution is limited to a narrow portion. When the energy distribution of ions is wide, each etching rate becomes the time average value, so that it cannot be set to the optimum value, and the selectivity is greatly reduced.

According to the experiment, if (V _DC / v _p ) is about 0.3 or less, the spread of ion energy is ± 15%.
It was below the level, and a high selection ratio was obtained with the characteristics shown in FIGS. Further, if (V _DC / v _p ) ≦ 0.5, the selection ratio and the like were improved as compared with the conventional sinusoidal bias method.

As described above, as a voltage suppressing means for suppressing the voltage change (V _CM ) during one cycle of the pulse voltage generated between both ends of the electrostatic adsorption film, V _CM is the magnitude v of the pulse bias voltage.
It is preferable that the thickness is set to be equal to or less than 1/2 of _p . Specifically, the thickness of the dielectric electrostatic chuck film 22 provided on the surface of the lower electrode 15 is reduced, By using a material having a high rate, the capacity of the dielectric can be increased. Alternatively, the cycle of the pulse bias voltage is set to 0.
1 μs to 10 μs, preferably 0.2 μs to 5 μs (corresponding to a repetition frequency of 0.2 MHz to 5 MHz), and the pulse duty (T ₁ / T ₀ ) is set to 0.05 ≦ (T ₁ /
T ₀ ) ≦ = 0.4 is set to suppress the voltage change across the electrostatic adsorption film.

Alternatively, by combining the film thickness of the electrostatic attraction film of the dielectric and some of the dielectric constant of the dielectric and the period of the pulse bias voltage, the voltage V _CM generated across the electrostatic attraction film is obtained. May satisfy the condition of (V _CM / v _p ) ≦ 0.5 described above.

Next, another embodiment in which the vacuum processing chamber shown in FIG. 2 is used for etching an oxide film (eg, SiO2, SiN, BPSG) will be described.

As the gas 19, C ₄ F 8: 1 to 5%,
_{Ar: 90~95%, O 2:} 0~5% _{or, C 4 F8: 1~5%,} Ar: 70~90%,
A composition having O ₂ : 0 to 5% and CO 10 to 20% is used. As the high frequency power source 16 for plasma generation, one having a higher frequency than the conventional one, for example, 40 MHz is used.
The discharge is stabilized in the low gas pressure region of 0 mTorr to 30 mTorr.

The modulation cycle of the high frequency power source for plasma source is usually longer than the cycle of pulse bias. Therefore, the modulation ratio of the high-frequency power source for plasma source is set to an integral multiple of the period of the pulse bias, and the phase between the two is optimized to improve the selection ratio.

On the other hand, the ion energy is controlled by accelerating and vertically injecting the ions in the plasma into the sample by applying the pulse bias voltage. As the pulse bias power supply 17, for example, a pulse cycle: T = 0.
By using a power source of 65 μs, pulse width: T ₁ = 0.15 μs, and pulse amplitude: Vp = 600 V, the ion energy distribution width becomes ± 15% or less, and
Plasma processing with a good selection ratio of 20 to 50 with respect to SiN or SiN has become possible.

Next, another embodiment of the present invention will be described with reference to FIG. This embodiment has the same configuration as the parallel plate electrode type plasma etching apparatus shown in FIG. 2, but the lower electrode 15 holding the sample 40 is provided with a unipolar electrostatic chuck 20. ing. That is, the lower electrode 1
A dielectric layer 22 for electrostatic attraction is provided on an upper surface of the DC power supply 5, and a lower side of the DC power supply 23 is connected to the lower electrode 15 via a coil 24 for cutting high frequency components. Also, 2
A pulse bias power supply 17 that supplies a positive pulse bias of 0 V to 800 V is connected via a blocking capacitor 19.

The sample 40 to be processed is placed on the lower electrode 15, and the electrostatic chuck 20, that is, the DC charge 23 supplies the positive charge and the negative charge supplied from the plasma to the electrostatic chuck film 22. It is adsorbed by the Coulomb force generated between both ends.

The operation of this apparatus is the same as that of the parallel plate electrode type plasma etching apparatus shown in FIG. 2. When performing the etching process, the sample 40 to be processed is placed on the sample table 15 and electrostatic force is applied. The pressure in the processing chamber 10 is reduced to 5 mTorr to 50 mTorr by introducing the processing gas from the gas supply system 36 into the processing chamber 10 at a predetermined flow rate while evacuating the chamber with the vacuum pump 18. Evacuate under reduced pressure. Next, the output of the high frequency power source 16 of 10 MHz to 500 MHz, preferably 30 MHz to 200 MHz is level-modulated by the high frequency power source modulation signal source 161, and applied between the parallel plate electrodes 12 and 15 to generate plasma. On the other hand, the lower electrode 15 is provided with pulse bias power supplies 17 to 20.
A positive pulse bias voltage of V to 800 V and a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs is applied,
The plasma in the processing chamber 10 is controlled to etch the sample 40.

The high-frequency power source 16 uses the high-frequency power source modulation signal source 161 to generate a pulse width of 1 to 50 μs and a pulse period of 40.
μs to 10 ms, pulse duty ratio (pulse width / pulse period) of 1/5 to 1/50 is pulse-modulated, and the instantaneous power of the pulse width portion is 2 to 100 times stronger than the instantaneous power of other timing portions. In addition, metastable atoms are efficiently generated in the pulse width portion. On the other hand, in the other timing portions, in the presence of the metastable atoms, high-frequency power having a relatively low instantaneous power is applied to promote ionization to obtain high-density plasma, and high energy of 15 eV or more. The generation of electrons is suppressed to prevent the excessive dissociation of the processing gas, and the dissociation is promoted at an electron energy of 10 eV or less, which is relatively low for plasma processing. As a result, the quantity and quality of ions and radicals can be controlled to desired values. Further, by applying a pulse bias voltage, ions in the plasma or ions and electrons are accelerated and vertically incident on the sample, thereby performing highly accurate shape control or selection ratio control. High frequency power supply 1
6, the characteristics required for the high frequency power supply modulation signal source 161, the pulse bias power supply 17, and the electrostatic adsorption film 22 are the same as those in the embodiment of FIG.

In another embodiment of the present invention described above,
Interference may occur between the output of the pulse bias power supply and the output of the plasma generation power supply. Therefore, the following will describe this measure.

First, in an ideal rectangular pulse having a pulse width: T ₁ and a pulse period: T ₀ and an infinite rise / fall speed, as shown in FIG. 11, f ≦ 3f ₀ (f ₀ = (1
/ T ₁ )) includes about 70 to 80% of the power. Since the actually applied waveform has a finite rise / fall speed, the power convergence is further improved, and f ≦ 3
The frequency range of f ₀ can include about 90% or more of electric power.

In order to uniformly apply a pulse bias having a high frequency component of 3f ₀ to the sample surface, a counter electrode substantially parallel to the sample is provided, and 3f ₀ obtained by the following equation 2 is obtained. Therefore, it is desirable to ground the frequency component in the range of f ≦ 3f ₀ .

[0103]

[Equation 2]

FIG. 12 shows an embodiment of the parallel plate electrode plasma etching apparatus shown in FIG. 2, in which measures against interference between the pulse bias power source output and the plasma generating power source output are taken. In this parallel plate electrode plasma etching apparatus, a high frequency power supply 16 for plasma generation is connected to the upper electrode 12 facing the sample 40. In order to bring the upper electrode 12 to the ground level of the pulse bias, the frequency f ₁ of the high frequency power source 16 for plasma generation is set to be larger than the above 3f ₀ , and the impedance in the vicinity of f ≦ f ₁ is large, so that other frequencies are not used. Then, the band eliminator 141 having a low impedance is connected between the upper electrode 12 and the contact level.

On the other hand, a bandpass filter 142 having a low impedance near f = f ₁ and a high impedance at other frequencies is installed between the sample stage 15 and the ground level. With such a configuration, the pulse bias power supply 1
The interference between the output of the sample 7 and the output of the power supply 16 for plasma generation can be suppressed to a level without any problem, and a good bias can be applied to the sample 40.

FIG. 13 shows an example in which the present invention is applied to a plasma etching apparatus of an inductively coupled discharge method and a non-magnetic field type among external energy supply discharge methods. 52
Is a flat coil, 54 is a flat coil with 10 MHz to 250 MHz
A high-frequency power source for applying a high-frequency voltage of z. The high-frequency power source modulation signal source 161 has a pulse width of 1 to 50 μs, a pulse period of 20 μs to 10 ms, and a pulse duty ratio (pulse width / pulse period) of 1/3 to 1/50. It is pulse-modulated, and the instantaneous power of the pulse width part is added with the strength of 2 to 100 times the instantaneous power of other timing parts.
Metastable atoms are efficiently generated in the pulse width portion. On the other hand, in the other timing part, a high frequency plasma of relatively low instantaneous power is applied in the presence of the metastable atoms to promote ionization and obtain a high density plasma,
The generation of electrons with high energy of 15 eV or more is suppressed to prevent excessive dissociation of the processing gas, and the dissociation with electron energy of about 10 eV or less, which is relatively low for plasma processing, is promoted. As a result, the quantity and quality of ions and radicals can be controlled to desired values. .

Compared with the parallel plate type shown in FIG. 10, the inductively coupled discharge method enables stable plasma generation at low frequency and low pressure. The processing chamber 10 as a vacuum container is
The sample table 15 on which the sample 40 is placed on the electrostatic adsorption film 22.
It has.

When performing the etching process, the sample 40 to be processed is placed on the sample table 15 and held by electrostatic force.
While introducing the processing gas from the gas supply system (not shown) into the processing chamber 10 at a predetermined flow rate, the pressure in the processing chamber 10 is reduced to 5 mTorr to 50 m by evacuating by the vacuum pump.
Evacuate to Torr. Next, the high-frequency power supply 54 outputs a high-frequency voltage of 13.56 MHz, which has been level-modulated, to the processing chamber 1
Plasma is generated at 0. The sample 40 is etched using the plasma. On the other hand, during etching,
A pulse bias voltage having a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs is applied to the lower electrode 15. The amplitude range of the pulse bias voltage varies depending on the film type, as described in the embodiment of FIG. By applying the pulse bias voltage, ions in the plasma are accelerated and vertically incident on the sample, thereby performing highly accurate shape control or selectivity control. Thus, even if the resist mask pattern of the sample is extremely fine, highly accurate etching can be performed.

FIG. 14 shows the induction-coupling type discharge type non-magnetic type plasma etching apparatus shown in FIG.
A Faraday shield plate 53 having a gap 55 and a thin shield plate protection insulating plate 54 of 0.5 mm to 5 mm are installed on the processing chamber side 10 of the induction electric high frequency output, and the Faraday shield plate 53 is grounded. By installing the Faraday shield plate 53, the capacitance component between the coil and the plasma is reduced, and the energy of the ions hitting the quartz plate under the coil 52 in FIG. 13 and the shield plate insulating plate 54 in FIG. 14 can be reduced. It is possible to reduce damage to the quartz plate and the insulating plate and prevent foreign matter from entering the plasma.

Further, since the Faraday shield plate 53 also serves as the ground electrode of the pulse bias power source 17, the pulse bias can be applied uniformly between the sample 40 and the Faraday shield plate 53. In the example of FIG.
No parallel plate type upper electrode or a filter installed on the sample table 15 is required.

Next, according to another embodiment of the present invention shown in FIG. 15, plasma etching which improves conventional defects, controls the amount and quality of ion and radical generation, and enables ultrafine plasma processing. Another embodiment of the apparatus will be described.

That is, on the upstream side of the vacuum processing chamber in which the sample is installed, a place where the first plasma is generated is set at a place different from the vacuum processing chamber, and the metastable atoms generated there are set in the vacuum processing chamber. The plasma is injected and the second plasma is generated in the vacuum processing chamber. In addition to the parallel plate plasma etching apparatus shown in FIG. 2, an ion / radical source gas supply unit 60 and a metastable atom generation plasma generation chamber 62 are provided. In addition to the route for introducing the gas containing metastable atoms into the vacuum processing chamber, the upper electrode 12 is provided with an introduction route connected to the gas supply unit for the ion / radical source.

The features of this embodiment are as follows.

The gas supplied from the metastable atom generation gas supply unit 36 is supplied to the metastable atom generation plasma generation chamber 62.
At high frequency, high frequency power is applied to generate plasma, and a desired amount of desired metastable atoms are generated in advance and flow into the processing chamber 10. The plasma generation chamber 62 for generating metastable atoms has a pressure of several hundred mT in order to efficiently generate metastable atoms.
Set to a high pressure of orr to several tens of Torr.

On the other hand, the gas from the ion / radical source gas supply unit 60 is caused to flow into the processing chamber 10.

The plasma generation power source 16 outputs a high frequency of relatively low power to generate plasma in the processing chamber 10. By implanting metastable atoms, ions can be efficiently generated even with low energy electrons of about 5 eV or less, so that low electron temperature (about 6 eV or less, preferably 4 eV or less) is obtained.
(eV or less) and a plasma having a high energy of about 15 eV or more and significantly less electrons can be obtained. For this reason,
The radical source gas does not cause excessive dissociation,
We can secure the necessary quantity and quality. On the other hand, the amount of ions can be controlled by the amount of metastable atoms generated in the plasma generation chamber 62 for generating metastable atoms and the ion source gas from the ion / radical source gas supply unit 60.

Since the quality and quantity of ions and radicals produced can be controlled in this way, good performance can be obtained even in ultrafine plasma processing. As the radical source gas, CHF3, CH2F2, C4F8 or CF
4 or other fluorocarbon gas, if necessary,
(C2H4, CH4, CH3OH, etc.). As the gas for generating metastable atoms, a gas based on one or two kinds of rare gases is used.
By using a rare gas or the like having the following properties as an ion source gas, ions can be efficiently generated.

With respect to the energy-level of the metastable atom,
A low ionization level of the ion source gas. Alternatively, an ion source gas having a higher ionization potential but a smaller difference (about 5 eV or less) is used.

Although the performance is deteriorated, the gas for metastable atom generation or the gas for radical source may be used as a substitute for the gas for ion source.

Next, FIG. 16 shows another embodiment of the present invention for controlling the quality and quantity of ion and radical formation. Although the basic idea is the same as that of FIG. 15, in FIG. This is an example implemented as a countermeasure. Reference numeral 41 is a magnetron as a microwave oscillation source, 42 is a microwave waveguide, and 43 is a first plasma generation chamber 45 which is vacuum-sealed.
Reference numeral 44 denotes a quartz plate for passing microwaves, and reference numeral 44 denotes a quartz plate for gas dispersion. In the first plasma generation chamber 45, plasma is generated by the microwave at a gas pressure of several hundred mTorr to several tens Torr, and metastable atoms are generated. In FIG. 16, the distance between the place where the metastable atoms are generated and the vacuum processing chamber can be shortened as compared with FIG. The amount of can be increased.
The processing chamber 10 is maintained at a pressure of 5 to 50 mTorr, and 20 MH
5 eV, preferably 3 e by a high frequency power source 16 of z or more
A high density low electron temperature plasma of 10 10 to 11 11 / cm 3 is generated at V or less, and the dissociation energy is 8
Ionization of the ion source gas is promoted while avoiding dissociation of CF2 that requires eV or more. As a result, the following reaction mainly progresses on the surface of the sample 40, assisted by the incidence of ions accelerated by the bias power supply 17 at several hundred volts.

SiO2 + 2CF2 → SiF4 ↑ + 2CO ↑ Since Si and SiN, which are the base materials, are not etched by CF2, the oxide film can be etched with a high selectivity.

The increase in F due to the partial dissociation of CF2 is reduced by the upper electrode cover 30 made of silicon, carbon, SiC or the like.

As described above, by adjusting the radical source gas and the ion source gas, the ratio of ions and radicals in the processing chamber 10 can be controlled almost independently, and the surface of the sample 40 can be controlled. It became easier to control the reaction of to the desired one.

The plasma processing apparatus of the present invention equipped with the electrostatic attraction circuit and the pulse bias voltage application circuit is limited to the above-described etching processing by making changes such as introducing the CVD gas instead of the etching gas. Instead, it can be applied to a plasma processing apparatus such as a CVD apparatus.

[0125]

According to the present invention, since the quality and quantity of ions and radicals produced can be controlled, processing conditions suitable for the object to be processed can be established.

By applying the bias of the present invention, the ions incident on the object to be processed can be accelerated with good controllability in a state where the energy distribution is narrow, and the selectivity and the processing speed of the plasma processing can be improved. It is possible to provide an improved plasma processing apparatus and plasma processing method.

When a sample table having a dielectric layer for electrostatic adsorption is used, the amount and quality of ions and radicals produced are controlled to obtain a narrow ion energy distribution with good controllability and the temperature of the object to be treated. It is possible to provide a plasma processing apparatus and a plasma processing method in which the surface reaction is controlled to be a predetermined temperature, the surface reaction is made uniform, and the performance is improved, and the selectivity and the processing speed of the plasma processing are improved.

Further, by controlling the quantity and quality of the generated ions and radicals, the pressure in the processing chamber of the plasma processing apparatus can be lowered to facilitate the precise processing of fine patterns, and the selection ratio during fine processing. It is possible to provide a plasma processing apparatus and a plasma processing method in which the above are improved.

By controlling the amount and quality of ions and radicals produced, the insulating film (eg SiO2,
It is possible to provide a plasma processing apparatus and a plasma processing method in which the selectivity of plasma processing with respect to SiN, BPSG, etc.) is improved without lowering the processing speed.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a difference in electron energy distribution.

FIG. 2 is a vertical sectional view of a parallel plate electrode type plasma etching apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a desirable output waveform used in the pulse bias power supply of the present invention.

FIG. 4 is a diagram showing a probability distribution of an ion energy and a potential waveform on a sample surface when T ₀ is changed while keeping a pulse duty ratio (T ₁ / T ₀ ) constant.

FIG. 5 is a diagram showing a potential distribution on a sample surface and a probability distribution of ion energy when T ₀ is changed while keeping a pulse duty ratio constant.

FIG. 6 is a diagram showing the relationship between the pulse off (T ₀ -T ₁ ) period and the maximum voltage V _CM during one cycle of the voltage generated across the electrostatic adsorption film.

FIG. 7 is a diagram showing a relationship between a pulse duty ratio and (V _DC / v _p ).

FIG. 8 is a diagram showing ion energy dependence of etching rates ESi and ESiO ₂ of silicon and a chloride film when chlorine gas of 5 mT is turned into plasma.

FIG. 9: CF4 gas 5 mT as an example of etching an oxide film
FIG. 3 is a diagram showing an ion energy distribution of an etching rate ESiO ₂ between an oxide film and silicon and ESi when plasma is generated.

FIG. 10 is a vertical cross-sectional view of a parallel plate electrode type plasma etching apparatus according to another embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between a frequency of a pulse bias power supply and accumulated power.

FIG. 12 is a vertical cross-sectional view of another embodiment in which the parallel plate electrode plasma etching apparatus shown in FIG. 1 is improved.

FIG. 13 is a vertical cross-sectional view of an example in which the present invention is applied to a plasma etching apparatus of an inductively coupled discharge method and a non-magnetic field type among external energy supply discharge methods.

FIG. 14 is a vertical sectional view of a plasma etching apparatus according to another embodiment of the present invention.

FIG. 15 is a vertical sectional view of a parallel plate plasma etching apparatus according to another embodiment of the present invention.

FIG. 16 is a vertical cross-sectional front view of a part of an apparatus in which the present invention is applied to a microwave + parallel plate plasma processing apparatus.

[Explanation of symbols]

10 processing chamber, 12 upper electrode, 15 lower electrode, 16
... high frequency power supply, 17 ... pulse bias power supply, 20 ... electrostatic chuck, 22 ... electrostatic attraction film, 23 ... DC power supply, 40 ...
Sample, 41 ... Microwave oscillation source, 42 ... Waveguide, 43 ...
Quartz plate, 44 ... Quartz plate for gas dispersion, 45 ... First plasma generating chamber, 161, ... High frequency power source modulation signal source.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuya Watanabe 794 Azuma Higashitoyo, Kudamatsu City, Yamaguchi Prefecture Stock company Hitachi Kasado Factory

Claims (12)

[Claims] 1. A vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, electrostatic adsorption means for holding the sample on the sample stage by electrostatic adsorption force, and the sample. A first plasma generating means for generating plasma inside or outside the vacuum processing chamber; and a second plasma generating means for generating plasma in the vacuum processing chamber. A plasma processing apparatus characterized by the above. 2. The plasma processing apparatus according to claim 1, wherein the instantaneous power supply of the first plasma generating means is at least twice and not more than 100 times the instantaneous power supply of the second plasma generating means. A plasma processing apparatus characterized by the above. 3. The plasma processing apparatus according to claim 1, wherein the power supply source of the first plasma generating means and the power supply source of the second plasma generating means are one pulse-modulated high frequency power source. A plasma processing apparatus characterized in that. 4. The plasma processing apparatus according to claim 1, wherein the pressure of the portion for generating the first plasma is set to be at least twice as high as the pressure for generating the second plasma. Plasma processing apparatus. 5. The plasma processing apparatus according to claim 1, further comprising pulse bias applying means for applying a pulse bias voltage to the sample, wherein the plasma generation source is 10 MHz.
A plasma processing apparatus characterized in that a high frequency voltage of up to 500 MHz is applied and the vacuum processing chamber is decompressed to 5 mTorr to 50 mTorr. 6. The plasma processing apparatus according to claim 5, wherein a pair of opposed electrodes on one side of which a sample is arranged,
During the etching of the sample, 250 V to
A pulse bias applying means for applying a pulse bias voltage having a pulse amplitude of 800 V and a duty ratio of 0.05 to 0.4 is provided, and the insulating film in the sample is processed using plasma in the vacuum processing chamber. A plasma processing apparatus having the above structure. 7. A step of placing a sample on a sample stage installed in a vacuum processing chamber, a step of holding the placed sample on the sample stage by electrostatic attraction, a step of introducing gas, and a step of introducing the gas. A first plasma-converting step of converting the generated gas into a plasma, and a second plasma-converting in an atmosphere in which the sample is disposed, containing at least the gas converted into a plasma in the first plasma-converting step. A plasma processing method comprising: a step of converting to plasma, a step of etching the sample with the plasma, and a step of applying a bias voltage to the sample during the etching. 8. The plasma processing method according to claim 7, wherein the instantaneous supply power of the first plasma conversion step is at least twice and not more than 100 times the instantaneous supply power of the second plasma conversion step. A plasma processing method characterized by being used in. 9. The plasma processing method according to claim 7, wherein the power supply source for the first plasma conversion step and the power supply source for the second plasma conversion step are one pulse-modulated high frequency wave. A plasma processing method characterized by using a power supply. 10. The plasma processing method according to claim 7, wherein the pressure of the portion for generating the first plasma is set to be at least twice the pressure for generating the second plasma before use. Plasma processing method. 11. The plasma processing method according to claim 7, further comprising a pulse bias applying step of applying a pulse bias voltage to the sample, wherein the plasma generating source includes a pulse bias applying step.
A plasma processing method comprising applying a high-frequency voltage of MHZ to 500 MHZ and depressurizing the vacuum processing chamber to 5 mTorr to 50 mTorr. 12. The plasma processing method according to claim 11, wherein a pair of opposed electrodes on one side of which a sample is arranged,
During the etching of the sample, 250 V to
A pulse bias applying step of applying a pulse bias voltage having a pulse amplitude of 800 V and a duty ratio of 0.05 to 0.4, and treating the insulating film in the sample with plasma in the vacuum treatment chamber. And a plasma processing method.