JPH10154699A - Remote plasma type plasma treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remote plasma type plasma treating device which can perform the etching of a fine pattern and the deposition of a film at a high speed without causing dielectric breakdown in an object to be treated nor giving any ion-impact damage to the object. SOLUTION: A remote plasma type plasma treating device is provided with plasma generators 11, 12, 13, 17, and 21 which generate plasma in a plasma generating space, a holder 16 which is arranged in a process chamber 15 continuously formed from the generators 11, 12, 13, 17, and 17 and on which an object 14 to be treated is placed, and a high-frequency power source 18 which impresses high-frequency power that is different from that for generating plasma upon the holder 16 and the frequency of the high-frequency power supplied to the holder 16 is set between 0.8MHz and 2.0MHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remote plasma type plasma processing apparatus, and more particularly, to a remote plasma type plasma processing apparatus which is used in a process of processing or depositing a sample using excited species generated by continuously generating plasma. The present invention relates to a remote plasma type plasma processing apparatus used in processes such as etching and deposition of various thin films in a device manufacturing process.

[0002]

2. Description of the Related Art Conventionally, a parallel plate electrode type plasma processing apparatus is generally used in a process of generating a plasma and processing or depositing a sample using excited species thereof. In a parallel plate electrode type plasma processing apparatus, high-frequency power is applied between a pair of electrodes placed parallel to each other in a vacuum vessel, and the gas introduced into the vacuum vessel is turned into plasma and applied to one of the electrodes. The mounted workpiece is processed. In the parallel plate electrode type plasma processing apparatus, ions in the plasma are accelerated by the difference between the plasma potential and the potential of the electrode, and are incident on the electrode surface. That is, in the present apparatus, the incident energy of ions is controlled by the high-frequency power applied between the electrodes, so that the number and energy of ions cannot be controlled independently. Further, in this device, a proportional relationship is not always established between the ion energy and the applied high frequency power.

As a method of overcoming the above-mentioned drawbacks of the parallel plate electrode type plasma processing apparatus and allowing desired ion energy, ion density, and active species density to be incident on an object to be processed, in recent years,
2. Description of the Related Art A plasma processing apparatus using remote plasma (hereinafter, referred to as “remote plasma type plasma processing apparatus”) has been proposed. This "remote plasma type plasma processing apparatus" has a mechanism for continuously generating plasma independently of the electrode on which the object is placed, and uses a high-frequency power applied to the electrode on which the object is placed to process the object. This is a plasma processing apparatus provided with a mechanism capable of controlling the energy of ions incident on the substrate to an arbitrary value.

FIG. 4 shows an example of a remote plasma type plasma processing apparatus utilizing helicon wave excitation, which is a kind of external electrode type high frequency excitation, as a continuous generation mechanism of plasma, as disclosed in US Pat. No. 4,990,229. 1 shows a processing device. In FIG. 4, a gas is introduced into the plasma generation chamber 51 by the gas introduction unit 50, and this gas is
A high-frequency electric field formed by supplying high-frequency power from a first high-frequency power supply 52 to an antenna 54 surrounding the plasma generation chamber 51 via a matching circuit 53;
It is converted into plasma by interaction with an axial magnetic field formed by the magnetic field coil 55. Next, the plasma is transported into another process chamber 56 along the magnetic field, and the workpiece 58 on the holder 57 is processed by the plasma.

[0005] In the apparatus shown in FIG.
The second high-frequency power supply 5
9 through the second matching circuit 60. Thereby, the workpiece 5
The energy of ions incident on 8 can be controlled to a desired magnitude.

Although the inventors of the above-mentioned apparatus do not particularly mention the frequencies of the first and second high-frequency power supplies, it is general that both the first and second high-frequency power supplies use a commercial frequency of 13.56 MHz. It is.

FIG. 5 shows an example of a remote plasma type plasma processing apparatus using electron cyclotron resonance as a continuous generation mechanism of plasma. In the device shown in FIG.
Electromagnet 6 installed outside plasma generation chamber 61
2 generates a magnetic field of 875 G in the plasma generation chamber 61, and generates electron cyclotron resonance with microwave power of 2.45 GHz introduced from the quartz window 63. At this time, by flowing an appropriate gas into the plasma generation chamber 61, plasma can be efficiently generated. The generated plasma is made to reach the holder 65 on which the object 64 is placed by diffusion, and desired processing is performed. The holder 65 is disposed in the processing chamber 66 below the plasma generation chamber 61. At this time, the high frequency power supply 67 and the variable capacitor 68 allow the ions in the plasma to enter the workpiece 64 with appropriate energy.
In general, high-frequency power having a frequency of several hundred kHz is applied to a holder 65 on which the object 64 is placed. In FIG. 5, reference numeral 69 denotes a microwave power supply, and reference numeral 70 denotes a gas introduction unit.

In the above-described apparatus, the energy of ions incident on the object 64 is controlled to an arbitrary value by the high-frequency power applied to the holder 65 on which the object 64 is mounted.
The number of incident ions is 2.4 introduced through the quartz window 63.
It can be controlled by microwave power of 5 GHz. It has been reported that 400 kHz is optimal as the frequency of the high frequency power to be biased. (S. Samukawa et al.
J. Vac.sci. Technol.B9 (3), May / Jun 1991)

[0009]

The above-described conventional remote plasma type plasma processing apparatus has the following problems.

In a conventional remote plasma type plasma processing apparatus, high-frequency power is supplied to a holder on which a workpiece is mounted for the purpose of controlling the energy of ions incident on the workpiece to an arbitrary value. The oscillating frequency of the high frequency power source is 13.56 MHz of commercial frequency or 400
A frequency of less than kHz or 400 kHz is common. When controlling the energy of ions incident on the object to be processed by the power of these frequencies, the larger the high-frequency power applied to the holder on which the object is placed, the more the electrical and physical damage to the object is caused. More likely to invite,
As the high-frequency power applied to the holder on which the object is placed is reduced, the possibility that the processing performance of the object is reduced is increased.

In a remote plasma type plasma processing apparatus, when high frequency power of 13.56 MHz is applied to a holder on which an object to be processed is mounted, the holder is compared with a resistance of a high frequency current flowing through the surface of the holder or the object to be processed. , The impedance of the ion sheath becomes very low.
Under such conditions, local discharge is likely to occur between the outer peripheral portion of the holder and the wall of the process chamber that is the ground electrode. Since the high-frequency current flows more in the portion where the local discharge has occurred, the high-frequency current flows more in the outer periphery of the holder than in the central portion, and the self-bias voltage distribution in the surface of the holder on which the workpiece is placed is reduced. The higher the part, the lower the center. If such a non-uniformity of the self-bias voltage distribution exists, the energy of the ions incident on the object to be processed may become non-uniform depending on the location, causing a problem that the processing speed of the object to be processed varies widely. Also, when the object to be processed is a semiconductor device, the amount of charge accumulated on the surface of the object to be processed becomes uneven, and a high voltage and a large current are excited in the circuit, thereby causing a problem of destruction of the element. Occurs. Furthermore, when the high-frequency power applied to the holder on which the object is placed is reduced so that the element is not destroyed as described above, a reduction in processing speed is inevitable. Furthermore, regardless of the magnitude of the high-frequency power applied to the holder, the energy of the ions incident on the object to be processed varies depending on the location, so that it is difficult to ensure a uniform processing speed.

On the other hand, in a remote plasma type plasma processing apparatus, when high frequency power of 400 kHz or less than 400 kHz is applied to a holder on which an object to be processed is mounted, for example, in an apparatus for performing an etching process in a semiconductor device manufacturing process, The atoms in the gas plasma are implanted into the Si crystal used as the substrate to be processed, thereby changing the electrical characteristics of the elements on the semiconductor device, and thus causing a problem of causing poor performance of the semiconductor device. This is because the energy of the ions accelerated in the above-mentioned frequency band tends to have a high or low range, and the high-energy ions therein contribute to the occurrence of ion impact damage due to the implantation of impurities as described above. . In order to prevent such a problem, it is effective to reduce the high-frequency power applied to the holder on which the object is placed, and to reduce the energy of all ions on average. However, in such a method, when the average energy value of the ions is equal to or less than a certain value, the etching process does not proceed at all, the etching process speed is significantly reduced with a decrease in the average energy value of the ions, and the area of the processed portion is reduced. However, the etching process of a high aspect ratio pattern having a large height and a large processing depth causes a decrease in the maximum processable aspect ratio, and significantly impairs the processing capability of the apparatus. That is, in a remote plasma type plasma processing apparatus that applies high-frequency power of 400 kHz or less than 400 kHz to an electrode on which an object is placed, even if the high-frequency power is set to any value, one or both of the conflicting demands are set. Has to be sacrificed to some extent.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is possible to perform etching of a fine pattern or deposition of a film at a sufficient processing speed without causing dielectric breakdown or damage due to ion bombardment in an object to be processed. An object of the present invention is to provide a remote plasma type plasma processing apparatus capable of performing processing.

[0014]

In order to achieve the above object, a remote plasma type plasma processing apparatus according to the present invention includes a plasma generation apparatus for generating plasma in a plasma generation space, and a plasma generation apparatus connected to the plasma generation apparatus. An object holder, which is placed in a vacuum vessel and on which an object to be processed such as a substrate is placed, and a high-frequency power supply means for applying a high-frequency power different from that for plasma generation to the object holder. And the frequency of the high-frequency power supplied to the workpiece holder is 0.8 MHz or more and 2.0 M or more.
Hz or less. The range of the frequency of the high-frequency power is particularly preferably from 1.0 MHz to 1.8 MHz.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 schematically shows a plasma etching apparatus using a helicon wave plasma source as a typical example of a remote plasma type plasma processing apparatus according to the present invention. In FIG. 1, an antenna 12 for generating a helicon wave excitation electric field and a magnetic field coil for forming an axial magnetic field necessary for exciting a helicon wave are provided around a plasma generation chamber 11 formed of a dielectric material. 13 are arranged. A gas introduction pipe 19 that can introduce gas into the process chamber 15 and the plasma generation chamber 11 is connected to the process chamber 15 connected to the plasma generation chamber 11. A holder 16 is provided in the internal space of the process chamber 15 so as to face the plasma generation chamber 11.
An object to be processed 14 is placed on 6. The holder 16
From the bias power supply high-frequency power supply 18 via the second matching box 20, for example, at a frequency of 1.6 MHz.
z high frequency power is applied.

The frequency of the high-frequency power applied from the bias power supply high-frequency power supply 18 to the holder 16 is preferably a frequency included in a range from 1.0 MHz to 1.8 MHz.

The object 1 to be processed is generated by generating plasma.
When performing the etching process on the process chamber 4, the process chamber 15 and the plasma generation chamber 11
The pressure is reduced to a required level by a well-known exhaust mechanism (not shown). Further, a process gas is introduced at a required pressure through a gas introduction pipe 19 by a gas introduction mechanism (not shown) into a process chamber 15 in which an etching process is performed on the workpiece 14.

The helicon wave exciting antenna 12 formed in a loop shape has a frequency of 13.56 MHz from a source power supply high frequency power supply 17 via a matching box 21.
Is supplied. The high-frequency power supplied from the high-frequency power supply 17 for source power supply is the source power supplied to the plasma generation chamber 11. The holder 16 is supplied with high-frequency power from the bias power supply high-frequency power supply 18 as described above. The high-frequency power supplied from the high-frequency power supply 18 for bias power supply is bias power for controlling the energy of ions incident on the workpiece 14, and the frequency is hereinafter referred to as “bias frequency”.

In order to prevent the plasma generated in the plasma generation chamber 11 from colliding with the inner wall surface of the process chamber 15 and losing the plasma, a rod-shaped permanent magnet (not shown) is provided outside the process chamber 15. )
It is also preferable to form a cusp magnetic field on the inner wall surface of the process chamber 15 by alternately arranging the magnetic poles.

In order to operate the plasma etching apparatus shown in FIG. 1, the plasma generating chamber 11 and the process chamber 15 are evacuated to a predetermined reduced pressure level by an exhaust mechanism. Next, C is supplied by a gas supply mechanism not shown.
Fluorocarbon gas such as F ₄ , CHF ₃ , C ₂ F ₆ , C ₄ F _{8 is} supplied through a gas introduction pipe 19 while controlling the flow rate by a mass flow controller (not shown). further,
A pressure control controller (not shown) controls a variable orifice (not shown) between the process chamber 15 and the exhaust mechanism to control the pressure within a range of 1 to 100 mTorr. At this time, an object to be processed 14, for example, a silicon wafer on which a desired pattern is formed with a resist on a silicon oxide film is placed on the holder 16. Holder 1
6 and the object 14 mounted thereon are cooled by an external cooler (not shown) through a cooling water introduction path (not shown) to prevent thermal damage to the resist due to a rise in temperature during processing. Can be. Next, source power is supplied to the antenna 12 via the matching box 21 by the high frequency power source 17 for supplying source power. At the same time, the holder 16
Is supplied with a required bias power from a bias power supply high-frequency power supply 18 in order to control the incident energy of ions to the workpiece 14.

In the above plasma etching apparatus,
As described above, the bias frequency of the high frequency power supplied from the bias power supply high frequency power supply 18 is 1.0 MHz.
It was set to be within the range of 1.8 MHz or less.

By setting the bias frequency to 1.8 MHz or less, the impedance of the ion sheath increases, and local discharge does not occur between the holder 16 and the wall serving as the ground electrode of the process chamber 15, so that the discharge is prevented. The high-frequency current flowing from the wall into the holder 16 is uniform over the entire surface of the holder 16 on which the workpiece 14 is placed, and is uniform over the entire surface of the workpiece 14 placed on the holder 16. A bias voltage is induced. Since the average value of the energy of the ions incident on the object to be processed 14 is nothing more than the sum of the plasma potential and the absolute value of the self-bias voltage, the distribution of the self-bias voltage is improved, so that the diffusion within the process chamber 15 is achieved. While maintaining uniformity of the ion current density in a plane parallel to the plasma holder 16 to be processed, ions can be incident on the object 14 with desired energy.

By setting the bias frequency to 1.0 MHz or more, the width of the energy of the ions incident on the object 14 can be set within 20% of the average ion energy. Bias power enough to raise the average ion energy to a level required for processing performance can be applied to the holder 16 without generating the ion energy.

FIG. 2 shows an opening diameter of 0.3 μm and a depth of 1.5 μm.
(33, 34) and the bias power density dependence of the thermal wave (TW) signal intensity of the silicon substrate exposed to plasma under the same conditions (33, 34). 3
1, 32). It is known that the correlation between the thermal wave signal intensity and the occurrence rate of lattice disorder and defects and the implanted concentration of impurity atoms is quantitative, and it is known that the greater the ion impact damage, the higher the thermal wave signal intensity. Yes (Allen Prosengwaig: Thermal
Wave Inspectionin IC Manufacturing, Mat.Res.Soc
Symp.Proc., Vol. 69 (1986) 111-125 Material Researc
h Society). In FIG. 2, solid lines 31 and 33 correspond to FIG.
Represents the results obtained in the silicon oxide film etching apparatus according to the present embodiment having the configuration shown in FIG. 7 and having a bias frequency of 1.6 MHz, and dotted lines 32 and 34 represent the results obtained in the conventional apparatus having the same configuration and the bias frequency of 400 kHz. Represents

When the bias frequency is 400 kHz, in the region where the bias power density is 3 W (watt) / cm ² or more, the thermal wave signal intensity is 500 or more, but the aperture diameter is 0.3 μm and the depth is 1.5 μm. 5 W / cm ² for etching to proceed in the contact hole
The above bias power density is required, and it is impossible to suppress ion impact damage and to process a fine pattern. On the other hand, in the plasma etching apparatus having the configuration shown in FIG. 1 and the bias frequency of 1.6 MHz, the thermal wave signal intensity satisfies 500 or less in the region where the bias power density is 6 W / cm ² or less and 4 W / cm ^2.
With a bias power density of not less than ² cm ² and an aperture diameter of 0.3 μm,
A practical etching rate can be ensured even in a contact hole having a depth of 1.5 μm. That is, in the plasma etching apparatus according to the present embodiment having the configuration shown in FIG. 1 and having a bias frequency of 1.6 MHz, it is possible to secure etching performance while suppressing ion impact damage.

FIG. 3 shows the dependence on the bias power density (35, 36) of the rate of occurrence of dielectric breakdown of an antenna MOS having an antenna ratio of 100,000 and an insulating film thickness of 10 nm, and the silicon on a silicon substrate exposed to plasma under the same conditions. Dependence of oxide film etching rate on bias power density (37, 38)
Is shown. In FIG. 3, solid lines 35 and 37 represent results obtained in the silicon oxide film etching apparatus according to the present embodiment having the configuration shown in FIG. 1 and a bias frequency of 1.6 MHz, and dotted lines 36 and 38 have the same configuration. The result in the conventional device with a bias frequency of 13.56 MHz is shown. In the case where the bias frequency is 13.56 MHz, dielectric breakdown starts to occur in a region where the bias power density is 2 W / cm ² or more, and in the region where the bias power density is 4 W / cm ² or more, 100% or less.
%, But a bias power density of 3 W / cm ² or more is required to progress the etching of the silicon oxide film, and it is impossible to etch the silicon oxide film while suppressing ion impact damage. In contrast,
It has the configuration shown in FIG. 1 and the bias frequency is 1.6 MHz.
In the etching apparatus, the bias power density is 6 W / cm.
^In a region of ² or less, no dielectric breakdown occurs, and the etching rate of the silicon oxide film is such that the bias power density is 4.
Saturates under the condition of 5 W / cm ² . That is, in the etching apparatus according to the present embodiment having the configuration shown in FIG. 1 and the bias frequency of 1.6 MHz, a sufficient processing speed can be obtained without causing charge-up damage.

In the above-described embodiment, an example of a silicon oxide film using a helicon wave plasma source has been described. However, the remote plasma type plasma processing apparatus according to the present invention is not limited to the above-described example. For example, in addition to an aluminum alloy or polycrystalline silicon etching apparatus, surface modification by plasma, plasma CVD, or the like can be used.
Of course, the present invention can be applied to remote plasma generating means other than the helicon wave plasma source, for example, ECR, TCP, ICP and the like. It is most preferable to use a high frequency power supply for bias of 1.6 MHz, and it is preferable that the bias frequency is 1.0 MHz or more and 1.8 MHz or less, and the same effect is obtained even if the bias frequency is 0.8 MHz or more and 2.0 MHz or less. You can expect to get.

[0029]

As apparent from the above description, according to the present invention, in a remote plasma type plasma processing apparatus,
Since the bias frequency of the high frequency power for bias applied to the holder and the workpiece is within a predetermined range, it does not cause dielectric breakdown damage or ion impact damage and has a sufficient processing speed for fine pattern etching and film deposition. Can be processed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a helicon wave plasma processing apparatus showing a typical embodiment of the present invention.

FIG. 2 shows the thermal wave (TW) signal intensity when the helicon wave plasma processing apparatus of the present embodiment is used and when the conventional helicon wave plasma processing apparatus is used, the opening diameter is 0.3 μm, and the depth is 1. 4 is a graph comparing the dependence of the etching rate of a silicon oxide film inside a 5 μm fine hole on bias power density.

FIG. 3 shows the dependency of the antenna MOS dielectric breakdown occurrence rate and the silicon oxide film etching rate on the bias power density when the helicon wave plasma processing apparatus of the present embodiment is used and when a conventional helicon wave plasma processing apparatus is used. 5 is a graph comparing.

FIG. 4 is a schematic configuration diagram of a conventional helicon wave plasma processing apparatus.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Plasma generation chamber 12 Antenna 13 Magnetic field coil 14 Workpiece 15 Process chamber 16 Holder 17 Source power supply high frequency power supply 18 Bias power supply high frequency power supply 20, 21 Matching box

Claims (1)

[Claims] 1. A plasma generator for generating plasma in a plasma generation space, a workpiece holder placed in a vacuum vessel continuous with the plasma generator and for mounting a workpiece, and the workpiece In a remote plasma type plasma processing apparatus including a high-frequency power supply unit for applying a high-frequency power different from that for plasma generation to a holder, a frequency of the high-frequency power supplied to the workpiece holder is 0.8 MHz. A remote plasma type plasma processing apparatus having a frequency of not less than 2.0 MHz and not more than 2.0 MHz.